PES Pre University College, Shivamogga · 7 + K2 KCl Cr O 7 +2 NaCl 1 1 1 24 i. What are interstitial compounds? ii. Transition metals show good catalytic property. Give any two reasons

Yogesh M, PES PUC Shivamogga [email protected] Page 1

R - X + 2 Na + X - RDry Ether

R - R + 2 NaX

Haloalkane Higheralkane

PES Pre University College, Shivamogga Chemistry (34 (NS)

(March 2019 Question Paper Key Answers) Yogesh M, Lecturer

PES PU College, Shivamogga

I Answer all the following in one word or in one sentence 10 X 1 = 10 1 How does the size of blood cells change when placed in an aquoseous solution

containing more than 0.9% o( m/v) sodium chloride ?

Shrinks.

2 How does the volume change on mixing two volatile liquids to form an ideal

solution?

ΔV = 0.

3 Draw a graph of λm V/s √푪 for acetic acid (Weak electrolytic) solution.

4 Unit of rate constant of a reaction is same as that of its rate. What is the order of

the reaction?

0 order.

5 Among physisorption and chemisorptions which one has higher enthalpy of

Adsorption?

Chemisorption or Chemical adsorption

6 What is the role of depressant ( NaCN ) in froth floatation method ?

It helps for selective prevention of froth formation

7 Name the noble gas having ns2np6 electronic configuration but doesnot have

d-orbital in its valence shell.

Neon or Ne

8 Write the general equation for Wurtz

reaction.


R - COOH R - CH2OHA

C12H22O11 + H2O C6H12O6 + C6H12O6

Sucrose

dil HCl

Glucose Fructose

9 What is reagent ‘ A ‘ used in following reaction:

LiAlH4 or Lithium aluminum hydride.

10 Which vitamin deficiency causes the diseases pernicious anaemia ?

Vitamin B12.

II Answer any five of the following 5 X 2 = 10

11

푑 =2푋7

(6.022푋10 ).(3.52푋10 )

푑 =14

(6.022푋10 ).(43.16푋10 )

Lithium metal has a body centered cubic lattice structure with edge length of

unit cell 352 pm. Calculate the density of Li metal. (Given atomic mass of

Lithium = 7 g/mol, NA = 6.022 X 1023 atoms per mol).

aNa

MZd 3

푑 =.

= 0.53 g/cm3

12 State Faraday’s second law of electrolysis. When same amount of electricity is passed to different electrolytes, then the mass of substances deposited or liberated at the electrode is directly proportional to its equivalent mass.

2

13 What is pseudo first order reaction? Give an example. A chemical reaction of higher order can be converted into first order by taking all the other reactants except one in larger excess called pseudo first order reaction.

Example: Inversion of cane sugar

1

1

14 How will you account for the following?


OH ONa OH

COONa

OH

COOH

+ CO2

NaOH

Sodium phenoxide Sodium salyciliate Salicylic acid

4 - 7 attm

H5C6 C

O

H + NaOH H5C6 CH2 OH + H5C6 C

O

ONaSodium Benzoate Benzyl alcohol

2Bezaldehyde

i. Actinoids exhibits more number of oxidation state than lanthanoids.

ii. Atomic radii of second and third transition series elements are

almost identical.

i. This is because energy difference in 5f, 6d and 7s orbitals of actinoids is smaller than 4f, 5d and 6s orbitals of lanthanoids.

ii. It is due to lanthanoid contraction.

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15 Explain the kolbe’s recation with equation. When phenol is treated with NaOH to yield sodium phenoxide, this on heating with CO2 at 400 K and 4 – 7 atm. Sodium salicylate is formed as a major product. This on acidification yields salicylic acid.

2

16 Write the equation for the reaction between benzaldehyde and conc.NaOH Solution. Name the reaction. Aldehyde having hydrogen (Acidic hydrogen) reacts with alkali like NaOH or KOH it forms salt of carboxylic acid and an alcohol is called cannizzaro’s reaction.

1

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17 i. What are Anionic detergents?

ii. What is the role of saccharin in food?

i. These are the detergents in which the larger part hydrocarbon chain of

detergent contains negative charge.

ii. Artificial sweetening agent.

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18 Give one example each for the following.

i. Ant fertility drug: Novestrol, Norenthindrone.

ii. Narcotic analgesics: Heroin, Morphine.

1 1

III Answer any five of the following 5 X 3 = 15 19 a) In the extraction of aluminum by electrolysis


i. Write overall cell reaction.

ii) What is role of cryolite?

b) Name the metal refined by Mond’s process.

2 Al2O3 + 3 C 4 Al + 3 CO2i.

ii. Decreases the melting point of the mixture or It increase the conductivity of the solution

b) Nickel or Ni

1 1 1

20 In the manufacture of ammonia by Haber’s process, write the flow chart and chemical equation with optimum conditions. In Haber’s process ammonia is manufactured by the reaction.

N2 + 3H2 2NH3 H ∆ = - QKJ.

Conditions for maximum yield of ammonia:

1. High pressure of 200 atoms.

2. Optimum temperature of 700K.

3. Use of Iron oxide catalyst mixed with (K2O + Al2O3) promoter.

1) A mixure of N2 and H2 in the ratio 1:3 is compressed to 200 atoms in the

compressor.

2) It is sent into the converter. Here N2 and H2reacts at 700K in the presence of

catalyst.

15% conversion occurs.

3) NH3 and unconverted N2 and H2are passed into cooler. Here NH3 liquiefies. N2 and H2 are recirculated.

1 1 1


OHOOH

S

. .

21 a) Give reason:

i. Hydrogen bonding in H2O but not in H2S.

ii. Conc. H2SO4 is god dehydrating agent.

b) Give the structure of sulphurous acid.( H2SO3)

i. Because sulphur is less electronegative than oxygen.

ii. Due to strong affinity for water, thus absorbs quickly.

b)

1 1 1

22 Complete the following chemical equations:

NH3 + 3 Cl2Excess

........... + 3 HCli )

ii ) Na2SO3 + 2 HCl +2 NaCl H2O + ...........

iii ) Br2 + 3 F2 ...........

i )

ii )

iii )

NCl3

SO2

2 BF3

1 1 1

23 Write the balanced chemical equation involved in the manufacture of Potassium dichromate from chromite ore? The ore is concentrated with soda ash (anhydrous Na2CO3) and pieces of quick lime in the presence of excess of air. The reaction occurs to give sodium chromate, ferric oxide and CO2 gas.

4 FeO Cr2O3 + 8 Na2CO3+ 7 O2 8 Na2CrO4 + 2 Fe2O3 + 8 CO2

The filtrated of sodium chromate is acidified with sulphuric acid to get sodium dichromate (orange red)

2 Na2CrO4 + H2SO4 Na2Cr2O7 + Na2SO4 + H2O

The filtrate is treated with potassium chloride to get potassium dichromate and sodium chloride.

Na2Cr2O7 + 2 KCl K2Cr2O7 + 2 NaCl

1 1 1

24 i. What are interstitial compounds? ii. Transition metals show good catalytic property. Give any two reasons.

i. The compounds in which small atoms like hydrogen, carbon, and nitrogen are trapped inside crystal lattice are called interstitial compounds.

ii. catalytic property due to (any two)

1


o Variable oxidation state. o Large surface area. o Presence of vacant d-orbitals. o Ability to form intermediate compound

2

25 a) Write the IUPAC name of K3[Cr(C2O4)3]. b) Give the facial ( fac) and meridional (mer) isomeric structures of

[Co(NH3)3NO2)3].

a. Potassium trioxalatochromate(III).

b.

1 2

26 With the help of VBT, explain hybridisation , geometry and magnetic property of

[Ni(CN)4]-2 ( Tetracyanidonickelate(II) ion), (Given atomic number of Ni=28). It can be shown by applying VBT.

E.C of Ni is [Ar]3d8 4S2E.C of Ni2+ is [Ar]3d8.

3d 4S 4P When 4CN-(strong) approach Ni2+ ion, the unpaired electrons get paired. One ‘d’ orbital becomes vacant.

3d dSP2 hybridization

After spin pairing ‘one 3d orbital, one 4s orbital and two 4P orbitals undergo hybridization to give 4 orbitals of similar shape and same energy. This is dsp2 hybridization. The 4 electron pairs from 4CN- ligands occupy dsp2 hybrid orbitals.

3d 4p dSP2 hybridized orbitals

1. All the electrons in the complex ion are paired. So the complex ion is diamagnetic.

1


2. Since dsp2 hybrid orbitals are involved, the shape is square planar.

NC

Ni

CN

NC CN

--- 2

Square Planar shape

1 1

IV Answer any three of the following. 3 X 5 = 15 27

푃푎푐푘푖푛푔푒푓푓푖푐푒푛푐푦 =푉표푙푢푚푒표푓푡ℎ푒푠푝ℎ푒푟푒푉표푙푢푚푒표푓푡ℎ푒푢푛푖푡푐푒푙푙 푋100

a) Calculate the packing efficiency of face centered cubic ( FCC) lattice.

Let the edge length be ‘a’

Let the radius of the particle (Sphere) be ‘r ’

The unit cell of Face centered cubic lattice contains four particle (Sphere)

Volume occupied by the 4 sphere = 4 X 휋푟 = 휋푟

Volume of the unit cell = a3

In the right angle triangle ABC

AC2 = AB2 + BC2

AC2 = a2 + a2 = 2a2 = √2 a

In HCC or CCP lattice, spheres on face diagonal touch each other AC = 4r 4r = √2 a a =

√

= /

√푋100 = 74

= 74% b) What is Frenkel defect? What is its effect on the density of solid?

The dislocation of cation from the crystal lattice to the interstitial site.

No change in density.

1 1 1 1 1


3 Mg + 2 Al+3 3 Mg

+2 + 2 Al

28

∆푻풇 = 푲풇 푾푿ퟏퟎퟎퟎ푴푿푽ퟐ

∆푻풇 = ퟐퟕퟑ −ퟐퟕퟏ.ퟏퟒ = ퟏ.ퟖퟔ

a) 31 g of unknown molecular material is dissolved in 500 g of water. The

resulting solution freezes at 271.14 K. Calculate the molar mass of material.

[ Give: Kf for water = 1.86 KKg/mol, Tf of water = 273 K ].

M= 푲풇 푾푿ퟏퟎퟎퟎ∆푻풇푿푽ퟐ .

= ퟏ.ퟖퟔ푿ퟑퟏ푿ퟏퟎퟎퟎퟏ.ퟖퟔ푿ퟓퟎퟎ

= 62 g/ mol

b) What is reverse osmosis? Mentions its use.

If the pressure applied on the solution is greater than the osmotic pressure then

solvent starts passing from solution into solvent is called Reverse Osmosis.

Use: Desalination of sea water.

29

(퐺푖푣푒푛:퐸 = −2.36푣, 퐸 = −1.66푉푎푛푑퐹 = 96487퐶

a) Write the equations for the reactions taking place at anode and cathode in

Lead storage battery.

b) Calculate the value of ΔrGo at 298K for the cell reaction ,

a) Anode : Pb + SO4

2- PbSO4 + 2e-

Cathode : Pbo2 + 4H++SO42- + 2e- PbSo4 + 2H2o

Net : Pb + Pbo2 + 4H+ + 2S)42- 2PbSo4 + 2H2O

b) ΔGo = - nFEo

= - 6 X 96487 X 0.7

= -405.2 kJ.

1

1

1

1

1

30 a) Derive an integrated rate equation for the rate constant of a first order reaction. Let us consider a First order reaction

P (R)

If the initial concentration of R is [R0] k is rate constant and [R] is the

concentration of R at time t. Then the differential form of this first order reaction will

be


−푙푛[푅] = kt − ln[푅 ].

푘푡 = ln[푅 ]. − ln[R]

푘푡 = ln[푅 ].

[R]

퐾2

퐾1= 4

.

. ( )

퐸 . .

퐸푎 = . .

푅푎푡푒 = − [ ][ ]

= k. dt

On integrating both side we get

∫ 푑 [ ][ ]

= ∫−푘푑푡

−푙푛[푅] = kt + c −−− −(1) ∵ ∫ 푑 [ ][ ]

= ln[푅]

퐴푡푡 = 0푎푛푑[푅] = 푅

Substituting the values in equation (1) we get,

−ln[R] = c

Substituting the value of C in 1 we get,

푐표푛푣푒푟푡푖푛푔 ln 푡표푙표푔

푘푡 = 2.303log [ ].

[ ] 푘 = . log [ ].

[ ]

b) The specific reaction rate of a reaction quadruples when temperature changes from 30oC to 50oC. Calculate the energy of activation of the reaction.[ Given: R = 8.314 J/K mol.]

푇 = 30 + 273 = 303퐾,푇 = 50 + 273 = 323퐾,

푇 −푇 = 323 − 303 = 20퐾


31

푥푚

= 푘푃

a) Define shape selective catalysis. Name the Zeolite catalyst used to converts

alcohols to gasoline in petrol industry.

b) What is peptization? Give an Example.

c) Write the expression for Freundlich adsorption isotherm.

a) The catalytic reaction which depends on the pore structure of the catalyst and size

of reactant and product molecules.

ZSM-5.

b) The process of converting freshly prepared precipitate in to colloidal solution by

adding suitable electrolyte.

Example: Ferric hydroxide sol.

c)

V Answer any four of the following 4 X 5 = 20


32 Write the equation for the steps involved in the SN1 mechanism of hydrolysis of

2-bromo-2methyl-propane.

Reaction occurs in two steps.

I Step: Heterolysis gives carbocation

Br

CH3

CCH3

CH3

CH3

C

CH3

CH3

++ Br

_

Carbocation

(rds)

II Step: Nucleophile OH-- attacks carbocation

OH

CH3

CCH3

CH3

CH3

CCH3

CH3

+ OH_

Carbocation

+

Tertiary butyl alcohol In rate determining step, one reactant molecule is involved. So the reaction

belongs to SN1 mechanism.

b) i. Name the product formed for the reaction of isopropyl iodide on alc.KOH.

Propene.

ii. What is the condition to be satisfied for a compound to be chiral?

The compound should at least contain one asymmetric carbon. or The four

valency of carbon must attached with different elements.

c) What is racemic mixture?

The Equimolar mixture of d and l isomers is called racemic mixture.

1 1 1 1 1

33 a) Explain the mechanism of acid – catalysed dehydration of ethanol to ethane.

I step: Protonation

Addition of proton to alcohol takes place.

CH3- CH2-OH + H+ CH3 – CH2 – OH2+

II step: Loss of water

CH3-CH2 – OH2+ CH3 – CH2

+ + H2O

III step: Loss of proton

H – CH2-CH2 CH2=CH2 + H+


CH3 - Cl + Na OC2H5 CH3 - O - C2H5 + NaCl

Methoxy Ethane

b) How do you prepare methoxy ethane by William son’s synthesis?

When an methyl chloride is heated with sodium ethoxide, methoxyethane is obtained.

34 a) How benzene does react with acetyl chloride in the presence of Anhydrous AlCl3?

Give equation.

b) i) Write general equation for Esterification reaction.

ii) Name the product obtained when benzoic acid is heated with Ammonia.

c) Name the reagent used in Clemmensen’s reduction.

a) Benzene reacts with acetyl chloride in the presence of Anhydrous AlCl3 yields Acetophenone.

AlCl3

C

O

CH3

Acetophenonebenzene

+ Cl C CH3

O

Acetyl Chloride

b) i)

R C

O

OH +H2SO4 O RR C

O

+ OH2

EsterH - O - R

C NH2

O

or Benzamide ii )

c) Zn-Hg/ Conc. HCl or Zinc-Amalgum and Conc. HCl.

2 1 1 1


CH3CONH2

Br2/Na

35 a) Between CH3NH2 and C6H5NH2, which is more basic and Give reason.

CH3NH2 is more basic

Because of +I – effect. Here no delocalization of electrons in ring

b) i) Name the main product when aniline is heated with alcoholic KOH and

Chloroform.

Phenyl isocyanide.

ii) Give the IUPAC name of ( CH3)2N-C2H5.

N,N – dimethylethanamine.

c) Complete the Chemical equation:

H3C C

O

NH2 + Br2 + 4 NaOH CH3 - NH2methyl amine

+ 2 NaBr + Na2CO3 + 2 H2O

Acetamide

1

1

1

1

1

36 a) Write the Haworth structure of maltose.

b) What is peptide linkage ? How many peptide bonds are present in a tetra-

peptide?

The –CONH- linkage between two amino acids is peptide linkage.

Three peptide bonds.

c) Name the Harmone which regulates blood sugar level in the body?

Insulin.

2

1

1

1

37 a) How is Buna-N prepared ? Give equation.

b) Name the monomers of Nylon-6,6.

2

2

Maltose D - Glucose + D - Glucose

CH2OH

H

OH

C

C

C O

C

C

H

H

H

OHOH

H

O

CH2OH

H

OH

OHC

C

C O

C

C

H

H

H

OH

H

D - Glucose D - Glucose


Hexamethylene diamine and adipic acid

c) What are thermosetting polymers ?

These are the polymers which becomes hard and infusible mass on heating due to

excess of cross-links and cannot be remoulded.

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Documents

PES Pre University College, Shivamogga · 7 + K2 KCl Cr O 7 +2 NaCl 1 1 1 24 i. What are interstitial compounds? ii. Transition metals show good catalytic property. Give any two reasons