Plus Two Chemistry 3m EM by Baskaran

8/12/2019 Plus Two Chemistry 3m EM by Baskaran

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P BLOCK ELEMENTS H 3PO 4 is triprotic. Prove.

It is tribasic acid. It combines with alkalies like NaOH to form three series of salts.

i) H 3PO 4 + NaOH NaH 2PO 4 + H 2O ii) H 3PO 4 + 2NaOH Na 2HPO 4 + 2H 2OSodium dihydrogen phosphate Disodium hydrogen phosphate

iii) H 3PO 4 + 3NaOH Na 3PO 4 + 3H 2OSodium phosphate

Prove that phosphorus acid is a powerful reducing agent? It is a powerful reducing agent because it has P-H bond. It reduces silver nitrate

solution into silver.2AgNO 3 + H 3PO 3 + H 2O 2Ag + H 3PO 4 + 2HNO 3

What is Plumbo solvency?Lead is not attacked by pure water in the absence of air, but water containing

dissolved air has a solvent action on it due to the formation of lead hydroxide (apoisonous substance) . This phenomenon is called Plumbo solvency .

2Pb + O 2 + 2H 2O 2Pb(OH) 2

Prove that P 2O 5 is a powerful dehydrating agent.Phosphorus pentoxide extracts water from many Inorganic and Organic compound.

H2SO 4 2 52

P O H O

SO 3

2HNO 3 2 52

P O H O

N2O5

RCONH 2 2 5

2

P O H O RCN

Why is HF is not stored in silica or glass bottles? Write the equations.It cannot be stored in glass or silica bottles as it attack silicates and silica

Na 2SiO 3 + 6HF Na 2SiF 6 + 3H 2OSiO 2 + 4HF SiF 4 + 2H 2O

Illustrate the oxidising power of fluorine.An important feature of the halogen is their oxidising property. Which is due to

high electron affinity of halogen atoms.The oxidizing power decreases from fluorine to Iodine.Fluorine is the strongest

oxidizing agent. It oxidises other halide ions to halogens in solution or when dry. F2 + 2X

- 2F - + X 2 (X- = Cl -,Br -, I -)

Write about the Holmes signal? Containers which have a perforated bottom and a hole at the top are filled with

calcium phosphide and calcium carbide.These are thrown into the sea, Water enters the container through the bottom and

reacts with calcium carbide and calcium phosphide to give acetylene and phosphine .Phosphine gets ignited spontaneously as it comes in contact with air and also ignitesacetylene.Thus a bright red flame is produced which is accompanied by huge smoke due to

the burning of phosphine.This serves as a signal to the approaching ships.Ca 3P2 + 6H 2O 2PH 3 + 3Ca(OH) 2CaC 2 + 2H 2O C2H2 + Ca(OH) 2

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Write the uses of Helium?1. Because of its lightness and non- inflammability helium is used to filling

balloons for meteorological observations.2.Because of its lightness it is used in inflating aeroplane tyres.3.A mixture of oxygen and helium is used in the treatment of asthma

How is ( K 2SO 4.Al 2(SO 4)3.24H 2O) potash alum prepared?Alunite or alum stone is K 2SO 4.Al 2(SO 4)3.4Al(OH) 3. It is finely powdered and

boiled with dilute sulphuric acid, the aluminium hydroxide part changes into aluminiumsulphate.When a little more potassium sulphate in calculated amount is added, the alum iscrystallised.

How is phosphoric acid prepared in the laboratory?Boiling a mixture of red phophorus with 50% nitric acid in a flask fitted with a

reflux condenser on a water bath till no more oxides of nitrogen are liberated. Iodine actsas a catalyst.The product is evaporated below 453K and then cooled in a vaccum desiccator surrounded

by freezing mixture when crystals of orthophosphoric acid are deposited.

P + 5HNO 3 2 /453 I K H3PO 4 + 5NO 2 + H 2O

Give three uses of neon.1.Neon is used in discharge tubes and fluorescent bulbs for advertisement display

purposes.2.Mixed with helium it is used to protect electrical instruments from high Voltages.3.Neon light is used in botanical gardens as it stimulates growth and helps the

formation of chlorophyll.

What are interhalogen compounds? Give the preparation of any one.Each halogen combines with another halogen to form several compounds known as

interhalogen compounds.They can all be prepared by direct combination or by the action of a halogen on a lower

interhalogen, the product formed depends on the conditions.

Cl2

+ F2

(equal volume) 473 K 2ClF

What is inert pair effect?One of the familiar characteristic of p-block elements is to show inert pair effect

that is the tendency of being less availability for ns electron in bonding . The inert paireffect increases down the group with the increase in atomic number.

What is the action of heat on phosphorus acid?When it is heated it undergoes auto-oxidation and reduction to form phosphoric

acid and phosphine.

4H 3PO 3 3H 3PO 4 + PH 3Phosphoric acid phosphine

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H 3PO 3 diprotic why?It is a dibasic acid and gives salts of two types.

ii) H 3PO 3 + NaOH NaH 2PO 3 + H 2O ii) H 3PO 3 + 2NaOH Na 2HPO 3 + 2H 2OSodium dihydrogen phosphite Disodiumhydrogen phosphate

Explain the action of heat on Orthophosphoric acid.2H 3PO 4 523 K H4P2O7 + H 2O ; H 4P2O7 589 K 2HPO 3 + H 2O

Pyro phosphoric acid Meta phosphoric acid

How are Xenon fluorides prepared? Xenon forms three binary fluorides XeF 2 , XeF 4 and XeF 6 by direct union of

elements under appropriate experimental conditions.673

2 2 K Xe F XeF ; 6732 42

K Xe F XeF 573

2 63 K Xe F XeF

Give the electronic structure of i) H 3PO 3 ii) PCl 5

d BLOCK ELEMENTSExplain Why Mn 2+ is more stable than Mn 3+ .

Electronic configuration of Mn 2+ is :[Ar] 3d 5 and Mn 3+ is: [Ar] 3d 4

Mn 2+ has 3d 5 electrons and d- sub-level is half filled . Mn 3+ has 3d 4 electrons and d-sub-level is neither half filled or completely filled . Half filled sub-level is more stable

due to symmetry. Therefore Mn 2+ is more stable than Mn 3+.

A substance is found to have a magnetic moment of 3.9BM. How many unpaired electrons does it contain?The magnetic moment = ( 2)n n BM n = number of unpaired electrons.

3.9 = ( 2)n n ; 3.9 = ( 2)n n ; (3.9) 2 = n (n+2)15 = n 2 + 2n ; n 2+2n-15=0 ; Solving this equation n = 3

Why do transition elements form complexes?i) Small size and high positive charge density.ii) Presence of vacant (n-1)d orbitals which are of appropriate energy to accept lone

pair and unshared pair of electrons from the ligands for bonding with them.

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Give any two evidences for the oxidizing nature of potassium dichromate.K 2Cr 2O7 + 7H 2SO 4 + 6KI 4K 2SO 4 + Cr 2(SO 4)3 + 3I 2 + 7H 2OIt oxidizes potassium iodide to iodineK 2Cr 2O7 + 7H 2SO 4 + 6FeSO 4 K 2SO 4 + Cr 2(SO 4)3 + 3Fe 2(SO 4)3 + 7H 2OIt oxidizes ferrous sulphate to ferric sulphate

Why do d-block elements have variable oxidation states. Give reason.i) These elements have several (n-1)d and ns electrons.ii) The energies of (n-1)d and ns orbitals are fairly close to each other.

How is chrome-plating done?i) The articles to be plated with chromium: Cathodeii) plate of lead : Anodeiii)Electrolytic bath contain : Chromic acid and Sulphuric acid.

During electrolysis chromium deposits on the article. Generally the articles are first platedwith nickel and then subjected to chromium plating.

Write the action of aqua regia on gold.Gold dissolves in aquaregia (3parts of Con.HCl+1part of Conc.HNO 3) to form auricchloride.2Au + 9HCl + 3HNO 3 2AuCl 3 + 6H 2O + 3NOCl

Auric chloride Nitrosyl chloride.What is spitting of silver? How can be it prevented?

Molten silver absorbs about twenty times its volume of oxygen which it againexpels on cooling .

Globules of molten silver are thrown off. This is called Spitting of silver. This can be prevented by covering the molten metal with a layer of charcoal.

What is the action of heat on copper sulphate crystals? Write the equation.

CuSO 4.5H 2O0

2

1004

C H O

CuSO 4.H2O0

2

230 C H O

CuSO 40720 C CuO + SO 3

Copper sulphate penta hydrate(Blue ) White Cupric oxide

What is action of zinc on hot NaOH solution? Zinc dissolves in hot NaOH solution forming soluble zincate ion.Zn + 2NaOH Na 2ZnO 2 + H 2

Sodium zincateWhat is the reaction of CuSO 4 with KCN?A yellow precipitate of cupric cyanide is first formed with KCN and it decomposes

to give cyanogen gas.CuSO 4 + 2KCN Cu(CN) 2 + K 2SO 4 ; 2Cu(CN) 2 Cu 2(CN) 2 + (CN) 2 Potassium cyanide Cupric cyanide Cuprous cyanide

Explain chromyl chloride test with equation.When salt containing chloride is treated with K 2Cr 2O7 and con.H 2SO 4 reddish

brown vapours of chromyl chloride are obtained.K 2Cr 2O7 + 4KCl + 6H 2SO 4 2CrO 2Cl2 + 6KHSO 4 + 3H 2O

ChromylchlorideThis reaction is used in the detection of chloride ions in qualitative analysis.

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Why are transition metal ions coloured?Most of the transition metal compounds are coloured in their solid or solution form.

The colour of transition metal ions is due to the presence of unpaired electrons in it andthe energy gap between two energy levels in the same d-subshell being small.Hence very small amount of energy is required for excitation of electrons from one energylevel to the other. The energy can be easily provided by the visible light.The colourobserved corresponds to the complementary colour of the light absorbed.

What happens when KI solution is added to an aqueous solution of copper sulphate .When KI is added to a solution of CuSO 4, a white precipitate of cuprous iodide is

produced.CuSO 4 + 2KI CuI 2 + K 2SO 4 ; 2CuI 2 Cu 2I2 + I2

Cupric iodide cuprous iodide

Why are Zn2+

salts colourless while Ni2+

salts are coloured?Zn2+ : 3d10 Ni 2+ : 3d 8

Zn2+ salts are white because of the absence of vacant d-orbitals to which electronscan be excited. In Ni 2+ these 2 unpaired electrons and the energy gap between two energylevels in the same d- subshell being small.Hence very small amount of energy is requiredfor excitation of electrons from one energy level to the other. The energy can be easily

provided by the visible light. The colour observed corresponds to the complimentarycolour of the light absorbed.How is Purple of Caussius prepared?

Purple of Cassius is prepared by mixing very dilute solution of gold chloride withstannous chloride solution.

3 2 42 3 2 3 AuCl SnCl Au SnCl The gold thus precipitated is adsorbed by stannic hydroxide formed by the

hydrolysis.

4 2 44 ( ) 4SnCl H O Sn OH HCl

CHEMICAL KINETICSGive any three examples for opposing reactions.

1. CO (g) + NO 2(g) kf

kr CO 2(g) + NO (g)

2. CH 2 3. 2HI (g)kf

kr H2(g) + I2(g)kf

kr CH 3-CH=CH 2

H2C CH 2

The initial rate of a first order reaction is 5.2X10 -6 mol.lit -1 sec -1 at 298K, When theinitial concentration of the reactant is 2.6X10 -3 mol.lit -1. Calculate the first order rateconstant of the reaction at the same temperature.

Solution: The initial rate of a first order reaction is = 5.2X10 -6 mol.lit -1 sec -1 The initial concentration of reactant, A = 2.6X10 -3 mol.lit -1

Rate = k X [A] ; Rate

k Initialconcentration

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5.2 10 . sec2 10 sec

2.6 10 . X mol lit

k X X mol lit

What are parallel reactions? Give an example. In these group of reactions, one or more reactants react simultaneously in two or more pathways to give two or more products . The parallel reactions are also called asside reactions .Ex.Bromination of bromobenzene

Br

Br+ HBr

Bro-dibromobenzene

Br 2 Br

+ HBr

Br p-dibromobenzene

Show that for a first order reactions time required for 99% completion is twice thetime required for 90% completion of the reaction.

2.303 log at k a x

; 99%2.303 100log

1t

k ; 90%

2.303 100log10

t k

. 99%90%

21

t t

; 99% 90%2t t

What are consecutive reactions? Give an example.The reactions in which the reactant forms an intermediate and the intermediate

forms the product in one or many subsequent reactions are called as consecutive orsequential reactions. In such reactions the product is not formed directly from the reactant.ROOC (CH 2)n - COOR 1

k ROOC-(CH 2)n COOH 2k HOOC (CH 2)n COOH

Ex.Saponification of diester in presence of alkali

Write the Arrhenius equation and explain the terms. k = Ae Ea/RT

k = rate constant ; Ea = activation energy A = frequency factor.R = gas constant ; T = temperature in Kelvin.

Define order of a reaction.The order of a reaction is defined as the sum of the powers of the exponential

powers to which each concentration term is raised in the experimentally determined ratelaw of a chemical reaction.

In general reaction, aA + bB products.Rate = k[A] p[B] q

Total order of the reaction n= p +q

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What are opposing reactions? Give an example.In opposing reactions the products formed react back simultaneously to form

the reactants . These reactions are also called as reversible reactions.1. CO (g) + NO 2(g)

kf

kr CO 2(g) + NO (g)

Define activation energy?The additional energy required by the molecules to attain the threshold energy in

addition to the energy of collo iding molecules is called as activation energy Ea.Activation energy = threshold energy energy of colloiding molecules.

What is pseudo first order reactions? Give an example.Thus in a second order reaction, when one of the reactant concentration is in

excess (10 to 100 times) of the other reactant , then the reaction follows a first orderkinetics and such a reaction is called pseudo-first order reaction.

CH 3COOCH 3 + H 2O H CH 3COOH + CH 3OHHydrolysis of ester in the presence of mineral acid.

Derive an equation for the half life period of a first order reaction.For first order reaction

1

2.303log

ak

t a x If amount reacted x = a/2 then t = t 1/2

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2.303 log / 2at k a a ; 1/ 2

12.303log2t k

1/ 21

0.693sect s

k

What are complex reactions? Give one example.Reactions which do not take place in a single step but take place in a sequence

number of elementary steps are called as complex reactions.Ex. Saponification of diester in presence of alkali

ROOC (CH 2)n COOR 1k

ROOC (CH 2)n COOH 2k

HOOC (CH 2)n COOH

The rate constant for a first order reaction is 1.54X10 -3sec -1. Calculate the half lifeperiod. k 1 = 1.54X10

-3sec -1

Half life period,1

1/ 2

0.693sec.t

k ; 1/ 2 3 1

0.6931.54 10 sec

t X

1/ 2 450sec.t

The half life period for a first order reaction is 20 seconds. Calculate its rate constant.

11/ 2

0.693seck s

t ; 1 0.693 sec20k s ; = 0.0346 sec.

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What are simple reactions?A simple reaction takes place in a single step. Simple reactions are also known as

elementary reactions. One step reactions are elementary reactions. No side reactions, products are directly formed from the reactants.

Ex. 2NO + O 2 2NO 2

HYDROXY DERIVATIVESHow can the consumption of alcohol by a person be detected? (or) write the breathanalysis test.

The breath analysis test for the detection of ethanol involves the oxidation ofalcohol in the breath of a person who has consumed alcohol, by acidic potassiumdichromate and observing the change in the colour of the chromium ion Cr (VI) fromyellow orange to Cr (III) which is blue green colour .

Why is glycol more viscous than ethanol?Because of the presence of two hydroxyl groups the intermolecular hydrogen

bonding is made much stronger . Hydrogen bond can be formed between both OHgroups resulting in a polymeric structure. This leads to high viscosity and boiling point.

O CH 2 CH 2 O H O CH 2 CH O

H H H HWhy methanol is miscible with water while iodo-methane is not?

Methanol (CH 3OH) is miscible with water because due to the presence of hydroxylgroup (-OH) it is able to form H-bonding with water.

But iodo methane (CH 3I) does not contain (-OH) group.Since it is not able to formH-bonding with water.

Give any three uses of benzyl alcohol.i) Used as a local anaesthetic in intravenous subcutaneous injections.

ii) as an antiseptic in ointments. iii) as esters in perfumery. ( Benzyl acetate hasfragrance of jasmine) iv) as benzyl benzoate in the treatment of asthma and whoopingcough.

How is phenolphthalein prepared?O

O=C C=O H OH O OHO=C C

2 4.Con H SO +H 2OH OH OH

Phthalic anhydride phenol phenolphthaleinHow will you convert C 2H 5OH to C 2H 5OC 2H 5? (or) Write dehydration reaction ofethyl alcohol.

Alcohols undergo intermolecular dehydration by treating with con.H 2SO 4 acid to

give ethers.C2H5OH + C 2H5OH

2 4

410.

K Conc H SO

C2H5 O C2H5

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What happens when glycerol reacts with KHSO 4 ?CH 2OH CH 2 CH 2

CHOH + 4 2 5 2 4( ) ( ) KHSO or P O or H SO C CH

CH 2OH CHOH CHO

Glycerol unstable acroleinTwo elimination reaction takes place to give acrolein or acrylic aldehyde

Explain Dows process. This reaction is an example of aromatic nucleophilic substitutionC6H5Cl + NaOH

623300

K atm

C6H5 OH + NaClThe replacement of nuclear halogen is difficult because of the stronger C-Cl bondcompare to that in alkyl halides.

Phenol is insoluble in NaHCO 3 solution but acetic acid is soluble. Give reason.Phenols are weakly acidic. These are stronger acids than alcohols but weaker than

all mineral acids,carboxylic acids and even carbonic acid.Hence phenols dissolve insodium hydroxide (a strong base) but not in sodium bicarbonate (weaker base). This

property is used in the separation of phenols from carboxylic acids.

Write the dye test for phenol.(or) Write note on coupling reaction.

N=N-Cl + OH 273OH

K N=N OH

Phenol couples with benzene diazonium chloride in alkaline medium to form p-hydroxy azobenzene. Diazonium ion C 6H 5N=N + is the electrophile in the reaction. Thisis also called dye test, which is characteristic of phenol.

How is allyl alcohol obtained from glycerol?At 533K, glyceryl dioxalate is formed which eliminates two molecules of

carbondioxide forming allyl alcohol.CH 2OH CH 2 - O CO CH 2

CHOH + (COOH) 2 533 K

CH O - CO CH + 2CO 2

CH 2OH CH 2OH CH 2OH

Alcohols cannot be used as a solvent for Grignard reagents. Why?Strongly basic substances like organometallic compounds are decomposed by

alcohol . Hence alcohols cannot be used as a solvent for Grignards reagents. R OH + CH 3MgBr RO Mg Br + CH 4

How is ethylene glycol converted into dioxan?HO- CH 2-CH 2-OH HO-CH 2-CH 2 CH 2-CH 2

+ 2 4.con H SO

O 2 4.con H SO

O OHO-CH 2-CH 2-OH HO-CH 2-CH 2 CH 2-CH 2

Ethylene glycol diethylene glycol dioxan

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Write note on Kolbes reaction. CO 2 is the electrophile in this reaction.

ONa OH OH

2

400 / 4 7CO

K atm COONa .dil HCl COOH+NaCl

Sodiumphenoxide Sodiumsalicylate Salicylic acid

How is glycerol synthesized from propylene?CH 2 CH 2 CH 2 CH 2OH CH 2OH

CH 2773Cl

K CH 2 3773 /12

Na CO K atm

CH HOCl CHCl NaOH CHOH + NaCl

CH 3 CH 2Cl CH 2OH CH 2OH CH 2OHPropylene allyl chloride allyl alcohol glycerol chlorohydrin glycerol

Give a chemical test to distinguish between ethanol and methanol.(or) Write a note oniodo form (haloform) reaction.

When alcohols containing CH 3CHOH group is treated with iodine and potassiumhydroxide,yellow crystals of iodoform is formed. Since methanol does not contain

CH 3CHOH group, it does not undergo halo form reaction.C2H5OH 2

/ I KOH CH 3CHO 2 I CI3CHO KOH CHI 3 + HCOOK

Write the conversion of ethylene glycol to 1,4 dioxan.HO- CH 2-CH 2-OH HO-CH 2-CH 2 CH 2-CH 2

+ 2 4.con H SO O 2 4.con H SO O OHO-CH 2-CH 2-OH HO-CH 2-CH 2 CH 2-CH 2

Ethylene glycol diethylene glycol dioxan

How is terylene prepared from glycol. Mention its use.

nHO CH 2 CH 2 OH+ HO-[-CH 2 -CH 2 O CO CO - O -] n H + (2n-1) H 2O

nHOOC C6H4 COOH terylene or dacron or tereneBoth glycol and dicarboxylic acid being molecules with two functional groups,

react forming condensation polymers. Use: synthetic fibre .

How will you convert 2-methyl-2-propanol into 2-methylpropene?OH CH 3

CH 3 C CH 3 /573Cu K dehydration C CH 2 + H 2O

CH 3 CH 3

Isobutylene

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What happens when ethylene reacts with cold dilute alkaline KMnO 4.

CH 2 CH 2 CH 2+ H 2O +(O) ' Baeyer sreagent

CH 2 OH OHEthylene ethylene glycol

Phenols are soluble in alcohols. Why?They are insoluble or sparingly soluble in water but dissolve readily in alcohol and

ether.Relatively high boiling point of phenols and solubility in alcohols can be explained

by intermolecular hydrogen bonding. Insolubility in water is explained by the presenceof hydrophobic phenyl group.

Starting from phenol how would you obtain picric acid.

OH OHO2 N NO 2

2 4 3

298. /

K Conc H SO HNO

+3H 2O

NO 2 Phenol picric acid (2,4,6 trinitro phenol)

How is benzyl alcohol prepared by Grignard Synthesis?Benzyl alcohol is prepared by the action of phenyl magnesium bromide on

formaldehyde.

36 5 6 5 2 6 5 2 ( )

H Oether C H MgBr HCHO C H CH OMgBr C H CH OH MgBr OH How is nitroglycerine prepared from glycerol?

CH 2OH CH 2 ONO 2

CHOH + 3HONO 2 2 4.Conc H SO CH ONO 2 + 3H 2O

CH 2OH CH2ONO2

NUCLEAR CHEMISTRYExplain the principle behind the Hydrogen bomb.

The principle behind the hydrogen bomb is nuclear fusion. The highly destructivehydrogen bomb is also based on the fusion reactions of hydrogen to form helium

producing large amount of energy.Hydrogen bomb consists of an arrangement for nuclear fission in the centre

surrounded by a mixture of deuterium and lithium isotope . Fission reaction providesthe high temperature necessary to start the fusion.

Fusion reaction take place in hydrogen bomb.` 1. Fission heat + neutrons

2. 3Li 6 + 0n1 1H3 + 2He4 +4.78 MeV3. 1H

2 + 1H

3 2He4 + 0n

1 + 17.6MeV

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What is the Q value of a nuclear reaction?The amount of energy absorbed or released during nuclear reaction is called Q- value ofnuclear reaction.

Qvalue = (m p-m r ) 931 MeV

m p = sum of the masses of productsm r = sum of the masses of reactants

Write are the difference between Chemical reactions and Nuclear reactions.

Chemical reactions Nuclear reactions1 The reaction involve some loss,

gain or overlap of outer orbitalelectrons of the reactant atoms

Nuclear reactions involve emission of alpha, beta and gamma particles from the nucleus.

2 A chemical reaction is balanced interms of mass only

Nuclear reaction is balanced in terms of bothmass and energy.

3 No new element is produced sincenucleus is unaffected.

New element / isotope may be producedduring the nuclear reaction.

The atomic masses of Li,He and proton are 7.01823,4.00387 and 1.00715 amurespectively. Calculate the energy evolved in the reaction, 3Li

7+1H1 2 2He

4+Energy(1amu=931MeV)

Solution:Mass of reactants = mass of Li + mass of H

= 7.01823 + 1.00715= 8.02538 amu.Mass of products = 2Xmass of He

= 2X4.00387= 8.00774 amu

Mass loss during change = (8.02538 8.00774)amu= 0.01764amu

Energy evolved during the reaction is = 0.0176 X 931 MeV.= 16.423 MeV.

Calculate the disintegration constant in seconds if half life period is 100 seconds.

1/ 2

0.693t

; 0.693100

= 0.00693sec -1

In the following radioactive decay 92X232 89Y

220 how many and particles areejected?

92X232 89Y220 + 2He 4 + 1e 0

Comparing mass number of both sides.232 = 220 + a4+ b0

4a= 232 220 = 12a= 12/4 = 3.

Comparing the atomic numbers92 = 89 + 2a+ (-1)b= 89 + 2a b

2a b = 92 -89 = 3

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2X3 b = 3 b = 6 3 = 3

Number of particles emitted = 3 Number of particles emitted = 3.

Calculate the number of and particles emitted when 90 Th 232 nucleus is converted

into 82Pb208 .

90Th232 82 Pb 208 + 2He4 + 1e 0 Comparing mass number of both sides.

232 = 208 + a 4+ bx0

4a 232 208 = 24a = 24/4 = 6.

Comparing the atomic numbers90 = 82 + 2a + (-1)b

= 82 + 2a b2a b = 90 -82 = 8

2X6 b = 8 b = 12 8 = 4

Number of particles emitted = 6. Number of particles emitted = 4.

Half life period of 79Au198 nucleus is 150 days. Calculate its average life.

= 1.44 X t 1/2 ; = 1.44 X 150 = 216 days

The decay constant for 6C14

is 2.31X10-4

year-1

. Calculate the half life period. = 2.31 X10 -4years -1

1/ 2

0.693t years

;

4

0.6933000

2.31 10 years

X

How many and particles will be emitted by an element 84A218 in changing to a

stable isotope of 82B206 .

84A218 82B

206 + 2He4 + 1e

0

Comparing mass number of both sides.218 = 206 + a 4+ b0

4a= 218 206 = 12a= 12/4 = 3.


= 82 + 2a b2a b = 84 -82 = 22X3 b= 2

b = 6 2 = 4 Number of particles emitted = 3. Number of particles emitted = 4.

Define half-life period.The time required to distintegrate one half of any radioactive substance is called

half life period. Half life period of a radioactive substance is independent of initialconcentration. It depends only on the disintegration constant.

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0.693t1/2 = = decay constant.

Calculate the Q value. 13Al27+2He

4 14Si30+ 1H

1 Q= 13Al27 =26.9815 amu , 14Si

30 =29.9738 amu, 2He

4 = 4.0026 amu and 1H1 = 1.0078 amu.

Q = (mp mr) 931 Mevm = ( 29.9738 + 1.0078) (26.98.9815 + 4.0026) = - 0.0025 amu.

Q = 0.0025 X 931 MeV ; = 2.329 MeV..Energy released in this reaction.

State two uses of radio carbon dating.i)carbon dating has proved to be a great tool for correlating facts of historical importanceii) it is very useful in understanding the evolution of life, and rise and fall of civilizations.

In the conversion of 92 U238

82Pb206 , calculate the number and particles

will be emitted.92U238 82Pb 206 + 2He 4 + 1e 0

Comparing mass number of both sides.238 = 206 + a 4+ b0

4a= 238 206 = 32a= 32/4 = 8.


= 82 + 2a b

2a b = 92 -82 = 102X8 b= 10 b = 16 10 = 6

Number of particles emitted = 8. Number of particles emitted = 6.

SOLID STATEWhat are superconductors? Give any one of its application.

The ability of certain ultra cold substances to conduct electricity withoutresistance is called super conductivity.This superconductivity state is a state in which a material has virtually zero electricalresistance. Substances having this property are called super conductors.

i) High efficiency ore separating machines may be built using superconductingmagnets.

What is meant by super conducting transition temperature?The super conducting transition temperature Tc of a material is defined as a

critical temperature at which the resistivity of the material is suddenly changed tozero . Thus at that temperature a material is changed from normal material tosuperconductor.

What is a vitreous state?Glasses are regarded as amorphous solids or super cooled liquids as well. Thus,glassy or vitreous state is a condition in which certain substance can exist, lying betweenthe solid and liquid states.

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Write note on molecular crystal.The lattice points in molecular crystals consist of molecules which do not carry

any charge . The forces binding the molecules together are of two types.They are i) Dipole dipole interaction ii) Vanderwaals forces . Dipole- dipole

forces occur in solids which consists of polar molecules e.g. ice . The Vanderwaals forcesare more general and occur in all kinds of molecular solids.

Write note on Frenkel defect. i) This defect arises when an ion occupies an interstitial position between the lattice

points.ii)This defect occurs generally in ionic crystals in which the anion is much larger in

size then the cation.iii)The crystal remains neutral since the number of positive and negative ions are

the same. Ex. AgBr.

How glasses are formed?When certain liquids are cooled rapidly there is no formation of crystals at a

definite temperature, such as occurring on slow cooling.The viscosity of the liquidincreases steadily and finally a glassy substance is formed.

Determination the number of CsCl units per unit cell. CsCl has BCC arrangement.The chloride ions are at the corners of a cube where as Cs + ions is at the centre of

the cube or vice versa. Each Cs + ion is connected with eight Cl - ions and each Cl - ionsis connected with eight Cs + ions.

Number of chloride ions per unit = Nc/8 = 8/8 =1 Number of cesium ion per unit = Nb/1 = 1/1 =1Thus number of CsCl units per unit cell is one.

Cs+ ions ; Cl - ions

State Braggs law. The fundamental equation which gives a simple relation between the wavelength of the

X-rays,the interplanar distance in the crystal and the angle of reflection,is known asBraggs equation.

n = 2dsin

n = order of reflection d = interplanar distance in the crystal = angle of reflection = wavelength of X-rays.

Sketch the following lattices 1.simple cubic 2.body centered cubic 3.face centeredcubic

Simple cubic Body centered Face centered

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What is the entropy change of an engine that operates at 100C when 453.6Kcal ofheat is supplied to it?

qrev = 453.6 K.cal = 453.6 x 1000 calT = 100 oC ; 273 + 100 = 373 K

S revqT

; S 1453.6 1000

1216.1373 X

calK

Calculate the molar heat of vapourisation of the ideal liquid CCl 4.(Bp. of CCl 4 76C and S=87.864J)

Hvap Svap = = 21cal.deg

-1mole -1 ; Hvap = Svap X Tb Tb

Hvap of CCl 4 = Svap X Tb = 87.86 X (76 + 273) = 30663.14 J mole-1.

H and S values of a reaction at 300K are -10K.Cal.Mole -1 and 20 Cal.deg -1mole -1 respectively. Calculate G value?

G = H - T SAt 300K G = - 10,000 20 X 300

= - 16,000 cals.mole -1.G = - ve , spontaneous reaction.

Give entropy statement of second law of thermodynamics. Write unit of entropy also.A process accompanied by increase in entropy tends to be spontaneous

Unit of entropy : heat x temperature -1 i) calories per degree per mole

ii)cgs unit of entropy = calk -1

iii) eu per mole iv) SI unit is JK -1

State troutons rule. The heat of vaporisation in calories per mole divided by the boiling point of the

liquid in Kelvin is a constant equal to 21 cal deg -1 mole -1 and is known as the entropy ofvapourisation.

vapvap

H S

Tb

= 21cal.deg -1mole -1

Calculate the entropy change involved in the conversion of 1 mole of ice at 0C and 1atm to liquid at 0C and 1 atm. The enthalpy of fusion permole of ice is 6008Jmole -1.

H2O (s) 273oO C K H2O (l)

Ice water liquid

11 16008 22.007

( ) (0 273) fusion

fusion

H Jmol S Jmol K

Tm K

Calculate the maximum % efficiency possible from a thermal engine operatingbetween 110C and 25C.

% efficiency = 1 21

[ ]T T T

X100 ; T 1 = 110+273=383 ; T 2 = 25+273 = 298

% efficiency =[383 298]

383X100

% efficiency = 22.2%

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What are spontaneous reactions?The term natural process means that the process is spontaneo us and does not need

to be induced. It takes place on its own accord.In order to find out whether a process is spontaneous or not, the entropy changes of

the system and the surrounding for the stipulated process is considered.S = +ve , the entropy of the universe increases.

Calculate the change of entropy for the process. H 2O 2(l) 2H 2O (vap) involving

H vap = 40850 Jmol-1 at 373K.

11 140850 109.51

373vap

vap

H Jmol S JK mol

Tb K

What are the nature of the reaction when i) 0G ii) 0G iii) 0G i) 0G , non spontaneous ii) 0G , spontaneous iii) 0G , equilibrium.

CHEMICAL EQUILIBRIUM IIThe equilibrium constant Kc for A (g) B (g) is 2.5 x10 -2. The rate constant of theforward reaction is 0.05 sec -1. Calculate the rate constant of the reverse reaction.

Solution; Given: Kc = 2.5 x 10 -2 ; K f = 0.05 sec-1

f c

r

K K

K ; f r

c

K K

K ; 2

0.052

2.5 10r K

X

Rate constant of the reverse reaction Kr = 2 sec -1

In the equilibrium H 2 +I 2 2HI the number of moles of H 2, I 2 and HI are 1,2,3

moles respectively. Total pressure of the reaction mixture is 60 atm. Calculate thepartial pressures of H 2, I 2 and HI in the mixture.Solution: H 2 + I 2 2HI

Number of moles of H 2 at equilibrium = 1 mole Number of moles of I 2 at equilibrium = 2 mole Number of moles of HI at equilibrium = 3 moleTotal number of moles of equilibrium = 1+2+3 = 6 moles

Mole fraction of H 2 =1

6 ; Mole fraction of I 2 =

2

6 Mole fraction of HI =

3

6

Partial pressure = Mole fraction x Total pressure

2 H P =1

6 x 60 = 10 atm ; 2 I P =2

6 x 60 = 20 atm ; HI P = 3

6 x 60 = 30 atm

State Le Chateliers principle.

If a system at equilibrium is subjected to a disturbance or stress, then the equilibriumshifts in the direction that tends to nullify the effect of the disturbance or stress.

Write the equilibrium constant Kc for the following reactions.a) 2H 2O 2(g) 2H 2O (g)+ O 2(g) b) CO (g) + H 2O (g) CO 2(g) + H 2(g).

22 2

22 2

[ ] [ ][ ]

H O O Kc H O ;

2 2

2

[ ][ ][ ][ ]

CO H Kc CO H O

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What happens when ng = 0, ng = -ve, ng = +ve in a gaseous reaction ?The relation between Kp and Kc isKp = Kc (RT) ng

i) when ng = 0, Kp = Kc ii) when ng = -ve, Kp < Kc iii) when ng = +ve , Kp>Kc

Define reaction quotient. How is it related to equilibrium constant?Reaction quotient, Q is defined as the ratio of product of initial concentrations of

products to the product of initial concentrations of reactants under non equilibriumconditions.When Q is greater than Kc, (Q>Kc) reverse reaction is favoured.When Q is lesser than Kc, (Q


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Define equilibrium constant? The equilibrium constant (Kc) represents the ratio of product of the molar

concentrations of the products to the product of the molar concentrations of thereactants at equilibrium condition . The concentration of each species is raised to the

power of number of moles present in the stoichiometric equation.Consider xA + yB mC + nD

[ ] [ ][ ] [ ]

m n

x y

C D Kc

A B

Dissociation of PCl 5 decreases in the presence of increase in Cl 2. Why?According to Le chatelier principle, increase in concentration of any one of the

reactants or products shifts the equilibrium more towards the opposite direction. So by

increasing the concentration of Cl 2, the equilibrium shifts in the reverse direction, that ismore of PCl 5 is formed. By increasing the presence of Cl 2, PCl 5 dissociation is decreased.

Why is equilibrium reaction refered to as dynamic equilibrium?Chemical equilibrium is dynamic when the forward and reverse reactions take

place endlessly and simultaneously with equal rates.

( ) ( ) ( )2 2 33 2

g g g N H NH find the value of ng, Kp and Kc write relationship

between them. ng = No.of moles of the products - No.of moles of the reactants.

ng = 2-4=-2. Kp=Kc(RT) -2 ; Kp


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What is Brownian movement ? Give reason. The continuous rapid zig-zag chaotic random and ceaseless movement executed by

a colloidal particle in the dispersion medium is called Brownian movement.This is due to the unbalanced bombardment of the particles by the molecules of thedispersion medium.

What is Tyndall effect?When a strong beam of light is passed through a sol and viewed at right angles, the

path of light shows up as a hazy beam. This is due to the fact that sol particle absorbs lightenergy and then emit in all directions. This scattering of light by the sol particle is calledTyndall effect.

Write any three difference between physical adsorption and chemical adsorption. Physical adsorption Chemical adsorption

1 The gas molecules are held on thesurface of the solid by weak Vanderwaals force.

The gas molecules are held on the surfaceof the solid by strong chemical bondformation.

2 Heat of absorption is small Heat of adsorption is large3 Reversible Irreversible

What are the general characteristics of a catalyst?i)Only a small quantity of catalyst is generally needed.

ii)A catalyst cannot initiate a reaction. The function of a catalyst is only to alter thespeed of the reaction which is already occurring at a particular rate.

iii)The catalyst is generally specific in its action.

What are lyophilic sols? Give an example.Colloidal solutions in which the dispersed phase has considerable affinity for the

dispersion medium are called lyophilic colloids. Ex. Gelatin, protein, and starch.

ISOMERISM IN ORGANIC CHEMISTRYMesotartaric acid is an optically inactive compound with asymmetric carbonatoms.Justify your answer.

Meso tartaric acid has two asymmetric carbon atoms, one asymmetric carbon atom

is dextrorotatory and the other leavorotatory-both rotating to the same extent in oppositedirections.

The net result is, that this isomer becomes optically inac tive and is called Mesoisomer. The optical inactivity of the Meso isomer is due to the internal compensation. It is due to the inherent symmetry in the molecule.

What are the condition for a compound to be optically active?i) At least one carbon atom that is bonded to four different atoms or groups, it is called

asymmetric carbon atom.ii) Asymmetric molecule is not superimposable on its mirror image.iii) Chirality is the essential and the sufficient condition for a molecule to optically active.

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Differentiate diasteriomers from enantiomers. Enantiomer Diastereomer

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Optical isomers having the same magnitude but different sign of optical rotation.

They have configuration with non-superimposable object mirror image relationship.

Separation of enantiomers is a tedious process

Differ in the magnitude of opticalrotation.

They are never mirror images.

Separation from the other pairs ofenantiomers is easy.

What is racemic mixture? Give an example.When equal amounts of d-isomer and l- isomer are mixed one gets a racemic mixture

and this process is called racemisation.

Ex. d and l - tartaric acid.What are optical isomers? Give an example.

The compounds having same molecular and structural formula but differ only inmagnitude of the optical rotation are called optical isomers. This phenomenon is known asoptical isomerism. Ex. d-lactic acid and l-lactic acid.

Write briefly on Racemic mixture with an example. When equal amounts of d-isomer and l- isomer are mixed one gets a racemic

mixture and this process is called racemisation. Ex. d and l - tartaric acid.A racemic mixture becomes optically inactive. Because, in this mixture rotation

towards clockwise direction by the dextro isomer is compensated by the rotation towardsthe anticlockwise direction by the laevo isomers.

Trans isomer is more stable than cis isomer. Why?In the cis-isomer, similar groups are very near to each other Vander waals repulsion

and steric hindrance make the molecule much unstable. In the trans-isomer, similar groupsare diagonally opposite to each other. Hence ther is no steric interaction. Generally transisomer is more stable than cis isomer.Label the following as E-Z isomers.

i) Cl Br CH 3 CH 2OH

C CZ isomer E - isomer

C C

H F HOCH 2 H.

ii) CH 3 Br CH 3 Br

C CZ isomer E - isomer

C C

CH 3 Br HOCH 2 H

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Distinguish Racemic and Meso form. Racemic form Meso form

i)It is a mixture that can be separated intotwo optically active form

It is a single compound and hence cannot be separated.

ii)Optically inactive due to externalcompensation

Optically inactive due to internalcompensation

iii) Molecules of isomers present are chiral Molecules are achiral

CARBOXYLIC ACIDSWhat is trans esterification?

In presence of a little acid, methyl acetate is cleaved by ethyl alcohol to form ethylacetate.

CH 3COOCH 3 + C 2H5OH 2 4.Conc H SO CH 3COOC 2H5 + CH 3OH

What is meant by esterification reaction? Write the equation. Carboxylic acid reacts with alcohols in presence of mineral acid as catalyst and

forms esters. This reaction is called esterification.CH 3COOH + C 2H5OH 2 4

.Conc H SO CH 3COOC 2H5 + H 2O

Give the source and trivial name of i) HCOOH ii) C 3H 7COOH iii) C 11H 23COOH .Formula Source Trivial name

HCOOH Red ant (formica) Formic acid

C3H7COOH Butter (Butyrum) Butyric acid

C11H23COOH. Laurel Oil Lauric acid

Write note on HVZ reaction.When the halogenation is carried out with halogen and phosphorous trihalide, this

reaction is known as Hell-Volhard Zelinsky reaction.RCH 2COOH 2 3

/ Br PBr RCH 2COBr RCHBrCOBr 2 H O RCHBrCOOH

Mention the uses of oxalic acid. i) for removing ink stains and iron stains. ii) as mordant in dyeing and calico printingiii) in manufacture of ink and metal polishes. iv) Redox titration.

Formic acid reduces Tollens reagent but acetic acid does not. Give reason. Formic acid is unique because it contains both an aldehyde group and carboxyl

group also. Hence it can act as a reducing agent. But acetic acid does not.O O

H C OH H C OH

Write the tests to identify salicylic acid.i) An aqueous solution of salicylic acid gives violet colour with neutral ferric chloride.

ii) It gives effervescence with the sodium bicarbonate.iii) It is soluble in sodium hydroxide and reprecipitated on acidification.iv) with bromine water the colour is discharged with the formation of white precipitate.

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Account the reducing nature of formic acid with suitable illustration.Formic acid is unique because it contains both an aldehyde group and carboxyl group also.Hence it can act as a reducing agent. But acetic acid does not.

O O

H C OH H C OH

Formic acid reduces ammoniacal silver nitrate solution to metallic silver.HCOOH + Ag 2O H 2O + CO 2 + 2Ag

What is the reaction of lactic acid with Conc.H 2SO 4? (or) How is cyclic ester (or)lactide formed.

O

H3C CHOH HO C = O H 3C CH C=O2 4 H SO

O=C CH- CH 3 O=C CH-CH 3

OH HO OLactide

How is methyl salicylate prepared?

OH OH3

2 4. /CH OH

Conc H SO +H 2O

COOH COOCH 3 Salicylic acid Methyl salicylate

How is asprin prepared? (or) What is aspirin? Give its use.Acetyl salicylic acid known as aspirin. It is used as an analgesic and antipyretic.

OH OCOCH 3 3 2( )CH CO O

COOH COOHSalicylic acid acetyl salicylic acid (or) aspirin

Write three tests to identify carboxylic acids.i) Aqueous solution of carboxylic acids turn blue litmus into red colour.ii)Carboxylic acids give brisk effervescence with sodium bi-carbonate due to the

evolution of carbon-di-oxide.iii)On warming carboxylic acids with alcohol and concentrated sulphuric acid it forms

ester which is identified from its fruity odour.

What is the reaction of lactic acid with dil.H2SO

4?

CH 3CH(OH)COOH 2 4.dil H SO CH 3CHO + HCOOH

Lactic acid is cleaved by dil.H 2SO 4 to acetic aldehyde and formic acid.

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Mention the uses of Benzoic acid.i) Benzoic acid is used as an urinary antiseptic.

ii) Sodium benzoate is used as food preservative.iii) It is used for the manufacture of dyesiv) Benzoic acid vapours are used to disinfect bronchial tube.

How is pyruvic acid prepared?

CH 3CH(OH)COOH2

2 2/ Fe H O CH 3COCOOH

CHEMISTRY IN ACTIONWrite a brief note on Buna-S rubber.

It is obtained by the polymerization of butadiene and styrene in presence of sodiummetal.

nCH 2=CH-CH=CH 2 + nCH=CH 2 Na -(-CH 2-CH=CH-CH 2-CH-CH 2-)n

C6H5 C6H5Butadiene styrene buna S

Use : It is used for the manufacture of tyres, rubber tubes and other mechanical rubbergoods

Write a brief note on Antiseptic. Antiseptic is a substance that rendors micro organisms innocuous by killing them

or preventing their growth. This term is used particularly for preparations applied to livingtissues.

Ex. i) Iodoform, CHI 3 is used as an antiseptic and its 1% solution is a disinfectant.ii) 0.2% solution of phenol acts as an antiseptic and its 1% solution is a disinfectant.

What are Chromophores? Give two examples.An organic compound appears coloured due to the presence of certain unsaturated

groups(the groups with multiple bonds) in it. Such groups with multiple bonds are calledchromophores. Ex.Azo -N=N- Polyene -(HC=CH) n- Carbonyl >C=O

What are anaesthetics? Give one example.The drugs which produce loss of sensation are called anaesthetics. They are

classified into two types.

i) General anaesthetics Ex. Ether ii) Local anaesthetics Ex. Chloroform, Nitrous oxide

In what way antacids are important.Quite often after eating oily and spicy food one may feel uncomfortable due to some

burning sensation in stomach or food pipe.This is due to the imbalance in the acidity in the stomach. Antacids provides relief fromsuch burning sensation. Ex. Aluminium hydroxide and magnesium hydroxide

Why are iodoform and phenolic solutions called antiseptic?1%solution of iodoform and 0.2%solution of phenol rendor micro organisms innocuous

by killing them or preventing their growth. Therefore they are called as antiseptics.

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Write note on antibiotics.Many microorganism (bacteria, fungi and moulds) produce certain chemicals which

inhibit the growth or metabolism of some other microorganism. Such chemical compoundsare known as antibiotics. Three main sources of antibiotics: Bacteria, Fungi,Actinomycetes. Ex.Penicillin

Give the preparation of Buna-N rubber. It is obtained as a result of copolymerization of two parts of butadiene with one part

of acrylonitrile in the presence of sodium metal. Use: it is used for the manufacture ofstorage tanks for the solvents.

2CH 2=CH-CH=CH 2 + CH=CH 2 Na -(-CH 2-CH-CH 2-CH-CH-CH 2-)n .

butadiene CN CH CH CN acrylonitrile

CH 2 CH 2Buna N How Nylon-66 is prepared? Give its use.

O O H H O O

n H2 N(CH 2)6 NH 2 +nHO-C-(CH 2)4-C-OH -(-N-(CH 2)6-N-C-(CH 2)4-C-) n-hexamethylenediamine adipic acid Nylon-66

It is obtained by condensing adipic acid with hexamethylenediamine with theelimination of water molecule. shows good resistance to abrasion. It is used in bristles for

brushes and in textile.

What are artificial sweetening agents? Give two example.Mono and disaccharides are sweet in taste. Sweetness is commonly associated withsugars.

However, certain organic compounds which have been synthesized in laboratories areknown to be many times sweeter than canesugar. Such compounds are called artificialsweetening agents or artificial sweetners. Ex. Saccharin, Dulcin , Nectarin.

Give any three characteristics of Dye.i) it should have a suitable colour ii) it should be fast to light

iii) it should be able to fix itself (or) be capable of being fixed to the fabric.iv) it should be resistant to the action of water,dilute acids and alkalies.

ATOMIC STRUCTURE IIState Heisenbergs Uncertainty principle.

It is impossible to measure simultaneously both the position and velocity (ormomentum) of a microscopic particle with absolute accuracy or certainty

.4h

x p x = uncertainty in the position of the particle

p = uncertainty in the momentum of the particle. What are the conditions for effective hydrogen bonding?

i) High electronegativity of the atom bonded to hydrogen atom so that bond is

sufficiently polar.ii) Small size of the atom bonded to hydrogen so that it is able to attract the bonding

electron pair effectively.

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What is bond order?Bond order may be defined as half the difference between the number of electrons

in bonding molecular orbitals (Nb) and the number of electrons in antibonding molecularorbitals (Na).

Bond order =1

2(Nb-Na)

What is the significance of negative electronic energy?The energy of an electron at infinity is arbitrarily assumed to be zero. This state is

called zero energy state.When an electron moves and comes under the influence of nucleus, it does some work andspends its energy in this process.Thus, the energy of the electron decreases and it becomes less than zero, it acquires anegative value.

Define hybridization.Hybridization is the concept of intermixing of the orbitals of an atom having nearlythe same energy to give exactly equivalent orbitals with same energy, identical shapes andsymmetrical orientations in space.

Why is He 2 not formed?Helium atom contains two electrons and Helium molecule contains four electrons.Electronic configuration of helium atom is 1s 2. and He 2 molecule is 2 * 2( 1 ) ( 1 ) s s

*1 s

1s 1s

He 1 s HeHe 2

Nb = 2 ; Na = 2Bond order =

2 20.

2 2 Nb Na Bond order for He 2 molecule is zero,this molecule

does not exist.

Distinguish between a particle and a wave.Particle Wave

1 Particle is localised Wave is delocalised

2 Particles do not interfere Wave interfere3 When a number of particles are

present in a given region of space,their total value is equal to theirsum

When a number of waves are present in agiven region of space, the resultant waves can

be larger or smaller than the individual wavesdue to interference.

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PERIODIC CLASSIFICATION IIWhy is the first ionization energy of Beryllium greater than that of Lithium?

Be atomic number:4 Li atomic number: 3The I.E of Be is greater than that of Li because the nuclear charge of Be is greater thanLi. Higher the nuclear charge, greater would be the force of attraction between nucleus andouter most electron. Hence, the first I.E of Be is than that of Li.

Why is electron affinity of fluorine less than that of chlorine?i) Because of small size of fluorine atom the 2p-subshell becomes compact. There occurs

repulsion among electrons of the valence shell and also with electron to be added. Thisrepulsion is responsible for less tendency of F- atom to accept electron.

ii) Because of small size of fluorine there occurs large crowding of electrons around thenucleus. This crowding is able to screen the nucleus. Because of this, effective nuclear

charge gets decreased. Thus, electron is having less attraction during addition henceelectron affinity gets decreased.

Explain why the first ionization energy of Be is greater than that of B.Be atomic number: 4 , Electronic configuration : 1s 22s2

B atomic number : 5 , Electronic configuration : 1s 22s22p1

Boron atom is having one unpaired electron in 2p-subshell. Be-atom is having pairedelectrons in the 2s-subshell.

As the fully filled 2s-subshell in Be-atom is more stable than B-atom due to symmetry,more energy would be needed to remove an electron from Be-atom. Hence, Be has high I.E

Compare the ionization energy of nitrogen with that of oxygen.7 N 1s 22s22px12py12pz1 8O 1s 22s22px22py12pz1 Ionisation energy of oxygen is less than that of Nitrogen. Nitrogen has half filled

electronic configuration and it is more stable. Nitrogen has stable electronic configuration, electron removal becomes difficult and so

Nitrogen possess more ionization energy. But oxygen is ready to loose one electron toattain the nearest stable half filled configuration.

So oxygen possess less ionization energy than Nitrogen.

Define Electron affinity.The electron affinity of an element may be defined as the amount of energy which is

released when an extra electron enters the valence orbital of an isolated neutral atom toform a negative ion.

Mention the disadvantages of Pauling and Mulliken Scale.The disadvantage of Pauling scale is that bond energies are not known with any

degree of accuracy for many solid elements.The disadvantage of Mullikens scale is that electron affinities with the exception of a

few elements are not reliably known.Ionisation energy of Ne is greater than that of Fluorine reason out.

Ne(Z = 10) ; 1s 22s22p 6 F(Z = 9) ; 1s 22s22p 5

The nuclear charge of Ne is more than that of F. Greater the nuclear charge, greaterwould be the force of attraction between nucleus and outermost electron. Hence, the firstI.E. of neon would be greater than that of fluorine.

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The electron affinities of beryllium and nitrogen are almost Zero. why?

Be (Z = 4) ; 1s 22s2 N (Z = 7) ; 1s 22s22p 3

Beryllium has fully filled 2s subshell which gives extra stability to the atom due tosymmetry. Nitrogen has half filled 2p orbital which gives extra stability. ThereforeElectron affinity are almost zero.

Why is ionization energy of fluorine greater than that of oxygen.F ( Z = 9) ; 1s 22s22px

22py22p z

1 O ( Z = 8 ) 1s 22s22px22py

12p z1

Fluorine is having more nuclear charge than oxygen, the nucleus of Fluorine will attractthe outer 2p electrons more firmly then oxygen. Therefore I.E. of Fluorine is higher thanthat of oxygen.

If the d(C-Cl) is 1.76 A o and r(Cl) is 0.99 A o , Find the radius of carbon atom.d(C Cl) = r(C) + r(Cl)

r(C) = d (C Cl) r (Cl)= (1.76 0.99) A o

r(C) = 0.77 A o

Calculate the effective nuclear charge experienced by the 4s electron in potassiumatom. (S = 16.8 )

The electronic configuration of potassium atom is : 19K = (1s2 ) (2s 2 2p6 ) (3s 23p6 )4s 1

Effective nuclear charge :Z * = (Z S )Z* = 19 [(0.85 X No. of electrons in (n-1) th shell) + (1.00 X total number of

electrons in the inner shells)]= 19 [(0.85 X 8 ) + ( 1.00X 10)]

= 19- 16.8 ; Z*

= 2.20

Calculate the electronegativity value of fluorine on Mullikens scale from thefollowing data, I.E of F = 17.4 ev/atom and E. A = 3.62 ev/atom.

. .2 2.8

I E E A Electronegativity

X ;

17.4 3.623.75

5.6 Electronegativity

Larger the size of atom, lesser is the ionization energy. Explain.The ionization energy decreases with the increasing size of atom. Larger the size of

atom, lesser is the ionization energy. This is due to the fact that electrons are tightly held insmaller atoms whereas in large atoms, electrons are held quite loose, that is to say lesserenergy is required for removal of electrons from larger atoms than smaller one. Henceionization energy is lower for larger atoms and higher for smaller atoms.

ELECTROCHEMISTRY IState Faradays first and second laws of electrolysis.

First law:The mass of the substance (m) liberated at the electrodes during the

electrolysis is directly proportional to the quantity of electricity (Q) that passes through theelectrolyte. m Q

Second law:When the same quantity of electricity passes through solutions of different

electrolytes, the amount of the substances liberated at the electrodes are directly proportional to their chemical equivalents.

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State Kohlrauschs law. At infinite dilution wherein the ionization of all electrolytes is complete, each ion

migrates independently and contributes a definite value to the total equivalent conductanceof the electrolyte

What is common ion effect? Give an example.The reduction of the degree of dissociation of a salt by the addition of a common-ion

is called the common-ion effect.Ex. NH 4OH NH 4

+ + OH -

When solid NH 4Cl is added to NH 4OH solution,the equilibrium shifts to left. Thereby theequilibrium concentration of OH - decreases. This procedure of reducing the concentrationof OH - ions is used in qualitative analysis.

Define equivalent conductance. Give the equation for it.Equi valent conductance (c) is defined as the conductance of an electrolyte solutioncontaining one gram equivalent of the electrolyte.

c = kXV mho m 2 (gm equiv) -1

where k is the specific conductance of the solution and V is the volume of thesolution that contains one gram equivalent of the electrolyte.

State Ostwalds dilution law. Ostwa lds dilution law relates the dissociation constant of the weak electrolyte with

the degree of dissociation and the concentration of the weak electrolyte.2

1C

Ka

Define electrochemical equivalent. What is its unit.

The electrochemical equivalent is the amount of a substance deposited by 1 amperecurrent passing for 1 second. Unit : Kg.coulomb -1

96495equivalentmass

Z

What is buffer solution? Give an example. (or) What do you understand by buffersolution.

A buffer solution is one which maintains its pH fairly constant even upon the addition

of small amounts of acid or base.Ex. Acid buffers (CH 3COOH + CH 3COONa) : Basic buffers (NH 4OH + NH 4Cl)

Define specific (k) and equivalent conductance. How are they related?The reciprocal of specific resistance is called as specific conductance (or) specific

conductivity. 1 11

ohm m

Equivalent conductance ( c ) is defined as the conductance of an electrolyte solutioncontaining one gram equivalent of the electrolyte.

Equivalent conductance is equal to the product of specific conductance of the

solution and the volume of solution that contains one gram equivalent of the electrolyte.c = XV

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Why does the metallic conduction decrease with increase in temperature?Metallic conduction decreases with increase in temperature due to the enhanced

thermal vibration of metal atoms disrupting the movement of electrons passing throughthem.

CARBONYL COMPOUNDSGive IUPAC name for the following: i) Crotonaldehyde ii) Methyl-n-propyl ketoneiii) phenyl acetaldehyde.

i)Crotonaldehyde 2-butenal ii)Methyl-n-propyl ketone 2-pentanoneiii)phenyl acetaldehyde phenyl ethanal

How does formaldehyde react with ammonia? (or) What is Urotropine? Give its use.6CH 2O + 4NH 3 (CH 2)6 N4 + 6H 2OHexamethylene tetramine is known as urotropine

This is used as Urinary antiseptic in medicine, in the name of Urotropine

How is acetophenone prepared by Friedel-Crafts method?H + ClCOCH 3 3

.anhyd AlCl COCH 3 + HClBenzene Acetyl chloride Acetophenone

This is an electrophilic substitution reaction. The electrophile CH 3CO+ is generated

by the Lewis acid AlCl 3 from acetyl chloride.

What is formalin? Write its use.40% aqueous solution of formaldehyde is known as formalin and is used as a

preservative for biological specimens and in leather tanning.

What is rosenmunds reduction? What is the purpose of adding BaSO 4 in it?CH 3- C=O + H 2

4

Pd BaSO

CH 3 C=O + HCl

Cl HBaSO 4 is used as a catalytic poison, to stop the reduction at the stage of aldehyde.

Otherwise, the aldehyde formed will be further reduced to primary alcohol.

Write two tests to identify aldehydes.i)They reduce ammonical silver nitrate to metallic silver

CH 3CHO + 2Ag+ + 3OH - CH 3COO

- + 2Ag + 2H 2O

ii)Fehlings solution to red cuprous oxide CH 3CHO + 2Cu

2+ + 5OH - CH 3COO - + Cu 2O + 3H 2O

iii)Aliphatic aldehydes restore the original colour of the Schiffs reagent. Explain halo form reaction with an example.

It undergoes halogenation at carbon atomCH 3 CO CH 3 + 3Cl 2 CCl 3 CO CH 3

NaOH CHCl 3 + CH 3COONaIn presence of NaOH, chloroform is formed.

Write briefly on clemmensons reduction. H3C H 3C

C=O + 4(H)/ Zn Hg

HCl

CH 2 + H 2OH3C H 3CAcetone propane

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When benzamide is treated with bromine and alkali gives compound A. Also whenbenzamide is reduced by LiAlH 4 compound B is formed. Find A and B. Write theequations.

C6H5CONH 2 2 Br KOH C6H5 NH 2 + CO 2 compound A : Aniline

[A]C6H5CONH 2 4

LiAlH C6H5CH 2 NH 2 compound B: Benzylamine[B]

C 6H 5CH 2NH 2 2 HNO A [ ]O B / Zn Hg HCl C. identify A,B and C.

C6H5CH 2 NH 2 2 HNO C6H5CH 2OH +N 2 compound A : Benzyl alcohol

Benzyl amine benzylalcohol [A] compound B : Benzaldehydecompound C : Toluene

C6H5CH 2OH [ ]O C6H5CHO / Zn Hg HCl C6H5CH 3 Benzaldehyde[B] Toluene [C]

An aromatic primary amine A with molecular formula C 6H 7N undergoesdiazotization to give B. B when treated with hypophosphorous acid gives C. IdentifyA,B and C.

C6H5 NH 2 + O=N-OH 273 HCL

K C6H5 N=N-Cl

Aniline[A] nitrous acid benzene diazonium chloride[B]C6H5 N=N-Cl 3 2

H PO

Cu C6H6 + N 2 + HCl

[C] Compound A : AnilineCompound B : Benzene diazonium chlorideCompound C : Benzene

An aromatic simplest nitro compound A on reduction using Sn and HCl gives B. Bundergoes carbylamines reaction identify A and B. Give any one use of compound A.

(or)Compound A is yellow coloured liquid and it is called oil of mirbane. A on reductionwith Sn/HCl gives B. B answers Carbylamine test. Identify A and B.

C6H5 NO 2 /( )Sn HCl

H C6H5 NH 2 + 2H 2O compound A : Nitro benzene

[A] [B] compound B : AnilineCompound [A] used to prepare explosives like TNT,1,3,5-trinitrobenzene.

An organic compound (A) with molecular formula C 6H 7N gives (B) with HNO 2/HClat 273K. The aqueous solution of B on heating gives (C) which gives violet colour withneutral FeCl 3. Identify the compounds A,B and C.

C6H5 NH 2 + O=N-OH 273 HCL

K C6H5 N=N-Cl

Aniline[A] nitrous acid benzene diazonium chloride [B]

C6H5 N=N-Cl 2boiled H O C6H5OH + N 2 + HCl[C]

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Compound A : AnilineCompound B : Benzene diazonium chlorideCompound C : phenol

Write a note on carbylamine reaction.CH 3 NH 2 + CHCl 3 + 3KOH CH 3 NC + 3KCl + 3H 2O

Methyl isocyanide ( offensive smelling)

Write the mustard oil reaction.CH 3 NH 2 + CS 2 2

HgCl CH 3 NCS + H 2SMethyl isothiocyanate ( pungent mustard like odour)

Write the schotten Baumann reaction.C6H5 NH 2 + ClCOC 6H5 NaOH C6H5 NHCOC 6H5

Aniline benzoyl chloride benzanilide

Write note on Gomberg Bachmann reaction.C6H5 N2Cl + C 6H6 NaOH C6H5 C6H5 + N 2 + HCl

biphenylThe above reactions do not follow strictly SN mechanism. Instead free radicals are

formed as intermediatesAn Organic compound A of molecular f ormula (C 2H 5ON) treated with Br 2/KOHgive B molecular formula (CH 5N). Identify A and B.Write the equation.

CH 3CONH 2 2 / Br KOH

CH 3 NH 2 + CO 2 [A] [B]

Compound A: acetamideCompound B: methyl amine

An organic compound A of molecular formula C 2H 5NO on treatment withNa/C 2H 5OH gives B (C 2H 7) and with Br 2/KOH gives C (CH 5N). Identify A,B andC. Explain the reactions.

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Na C H OH CH CONH CH CH NH H O Compound A: Acetamide

Acetamide [A] Ethylamine [B] Compound B: Ethylamine

/3 2 3 2 2

Br KOH CH CONH CH NH CO Compound C: Methylamine

Methylamine [B]

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Plus Two Chemistry 3m EM by Baskaran