Some exams questions and answers

1-Which of the following does not represent a chemical change?

A)iron rusting B)reaction of sodium metal with water C)dissolving sugar in water D) souring of milk

F)leaves changing color

C) dissolving sugar in water

2-Which of the following does not represent a physical property:

A) boiling point B) odor C) density D) reaction with oxygen. F) solubility in water

Indicate the numbers of protons, neutrons and electrons in the following atoms:

, , ,

A-1 -

Am: 95 protons, 95 electrons, 148 neutrons

C : 6 protons 6 electrons 8 neutrons

Ag: 47 protons 47 electrons 62 neutrons

Zn: 30 protons 30 electrons 34 neutrons

Calculate the molecular mass of each of the following: Li2O, C3H7Br, (CH3CH2CH2)2O, KHSO3, N2O5,

KNO2

(a) -Li2O= (7x2) + 16 = 30 g (b) -C3H7Br = (3x16) + (7x1) + 80= 123 g(c) -(CH3CH2CH2)2O = 102 g (d) -KHSO3 = 39 + 1 + 32 + ( 3x16) = 120 g(e) -N2O5 = ( 2x14) + (sx16) = 108 g(f) -KNO2= 39 + 14 + (2x16) = 85 g

-Calculate the number of moles of CO present in a 125 g sample of

the gas. ) (6 marks)number of moles = mass in grams/molar mass

number of moles of CO = 125/28 = 4.464 mol

Answer whether each of the following statement is true or false:

(Answer 5 only )(15 marks)

a. Bases react with many metals to produce ionic compounds and hydrogen gas. ( false) b. The molarity (M) so called molar concentration.( true ) c. Within a group, electronegativity increases from bottom to top.( true) d. Dilution increases the volume of a solution.( true) e. Acids turn the color of the indicator litmus from red to blue.( false) f. Matter is anything that has mass and occupies a size of space.( true)

5. The metal indium melts at 156ºC. The boiling point of the organic liquid cyclohexanol is 321 ºF. Will indium melt in boiling cyclohexanol? ) (6 marks)F⁰ = ( C⁰ x 1.8 ) + 32 F⁰ = ( 156 x 1.8 ) + 32 = 280.8 F⁰ yes Indium will melt in boiling point of cyclohexanol

6. Determine which of the following represent elements and which do not.

C, CO, Cl, CaCl2, Na, KIC , Cl , Na : are elements , CO , CaCl₂ , KI : are not

7. Which of the following pairs of symbols represent isotopes?

(4 marks )

and , and , and

and , and

and are isotops

8. What are the names and symbols of the SI base units for length,

mass and time?

mass = kg , time = second9. Write: (10 marks)

a) The molecular formula of Phosphorus Pentachloride b) The name of SF6.

)a - (phosphorus pentachloride PCl₅

)b – (sulphur hexafluoride SF₆

10 .Which of the following does not represent a physical property?

A) color B) clarity C) hardness D) melting point E) flammability

E) flammability does not represent a physical property 11 .In the metric system, the prefix micro represents the

multiple A) 10-1. B) 10-2. C) 10-3. D) 10-6. E) 10-9.D)- 10-6.

4-How many g in 580.4 mg?

0.5804 g

5-Which metric prefix would replace the power of ten in 3.68x10ˉ³ m?

3.68 mm

6-Convert 184⁰F to Celsius.

C⁰ = F⁰ - 32/1.8C⁰ = 184-32/1.8 = 48.44

12 .During the course of a day, the difference between the highest and

the lowest temperature for the day was 9°C. What was the

temperature variation in °F? A) 5

B) 9.3 C) 16.6 D) 25.7

E) 34 F) 48.2

°F = (°C x 1.8 ) + 32 °F = ( 9 x 1.8 ) + 32 = 48.2

7-What is the volume in L of 64.0 fluid ounce bottle? (1L=1.o6qt) and (1qt=32fl.oz).

Number of 13 .Which of the following does not vary with

temperature? A) volume

B) mass C) density

D) Kelvin E) °C

B) mass 14 .Aqueous HI is known as

A) hydroiodic acid. B) hydrogen iodide.

C) helium iodide. D) hydrogen monoidide.

E) hyperiodous acid.A) hydroiodic acid.

15 -What the PH of 0.001 M solution of hydrochloric acid?

PH= - log [ H⁺ ]

PH= - log [ 10ˉ³ ]

PH= 3

16 -Calculate the PH value of a solution of sulphoric acid containing 4.9 g per liter of the acid?

-the molar concentration of the acid = 4.9/98=0.05-the molar concentration of hydrogen ions [ H⁺ ]= 0.05 x 2 = 0.1 mol/lit

PH = - log [10ˉ¹]PH= 1

17 -Calculate the PH value of 0.004 solution of acetic acid, where the ionization ratio constant (α) is 25%.

[H⁺ = ] M x α

[H⁺ = ] 0.004 x 0.25 = 10ˉ³PH= - log [ H⁺ ]PH = - log [ 10ˉ³ ]PH = 3

18 -Calculate the PH value of 0.001 M solution of sodium hydroxide?

[OHˉ = ] 10ˉ³

POH = - log [ OHˉ ]POH = - log [ 10ˉ³ ]POH = 3We know that : PH + POH = 14So we write:

PH + 3 = 14PH = 11

Q1-Answer only 15

1)-Which of the following is the correct formula of copper(1) oxide?

a)CuO b)Cu₂O c) Cu(OH)₂ d)Cu₂O₃ e) CuO₂

2)-which of the following is not a physical property?

(a)solid sulphur is yellow

(b)diamond is highly hard

(c)solid iron(Fe) melts at 1533Cº

(d)carbon reacts with oxygen to form carbon dioxde (CO₂)

3 -)What is the right name of the following compound:

BaCl₂

a)Bromuim Chloride , b)Barium Chloride , c)Barium Dichloride

d)Barium(11)Chloride

4-)Which of the following compounds are insoluble in water:

a) CaCl₂ b) NaCl c)Fe(OH)₃ d)FeCl₃ e)Pb(NO₃)₂

f) Ag₂SO₄

5-)Regarding the following reaction, which statement is incorrect?

Cu + 2Ag⁺ → Cu²⁺ + 2Ag

a)copper is oxidized b)copper is reduced c)Ag⁺ is reducing agent d) silver is oxidized

6-)Which of the following has the highest ionization energy value:

a) Cu , b) F , c)Na , d) C , e)O

7-)Which of the following orbitals fills first:

a) 3d b)3p c)4f d)3s e)4d

8 -)Which of the following is the best electrical conductor:

a) 0.6 M HNO₃ b)0.4 M CH₃COOH , c) 1.0 M CH₃CH₂OH d)0.14 M HCl e)0.8 M H₂SO₃

f) 0.80 M NH₄OH

9 -)Predict which of the following bond is the shortest:

10-)Which of the following is the correct Lewis symbol for an atom of Cl:

11)Which of the following bonds is the most polar bond:

a)C-O b)NaBr c)N-O d)Cl-Cl e)S-O

12)- Indicate the oxidation number of the underined atom in each of the following:

a)KMnO₄ b)Mg(ClO₄)₂ C)K₂Cr₂O₇

13)- Which of the following diagrams is not allowed:

14)-Given the following equation:

2H₂(g) + O₂(g) → 2H₂O(l) ΔH⁰ =-571.6kJ/mol

Which statement is incorrect?

a) ΔH⁰ for the reverse reaction is + 571.6 kJ/mol

b) ΔH⁰ for the forming one mole of liquid water is -285.8 kJ/mol

c) ΔH⁰ for the reaction of one-half mole of oxygeb is -285.8kJ/mol

d) The equation forming gaseous water would have different ΔH⁰

e) The standard heat of formation of liquid water is -571.6 kJ/mol.

15)-How many protons, electrons and neutrons are there in the following atoms:

16)- The emperical fornula of dichloro butane is C₂H₄Cl and its molecular mass is 127 u , what is the molecular formula?

17- calculate the formal charge of the nitrogen atom in the compond:

Q2- Identify if the following statements are correct or wrong.

1-( ) the chemical property displayed by the matter as it does not undergo any change in the composition.

2-( ) kandela is a SI unit

3-( ) electron affinity is the energy required to remove one electron from an isolated atom at the gas state and ground state.

4-( ) work is the transfer of energy between the system and its serroundings.

5-( ) the isotopes are atoms of different atoms having the same mass number and different atomic number.

Q2- Follow the instruction given for each question and answer the following :

a- Calculate the consumed amount and the remaining amount of oxygen during the reaction of 14.4 g of C₅H₁₂ in 100 g of oxygen :

C₅H₁₂ + O₂ → CO₂ + H₂O

Answer:

1- we have to balance the equation:

C₅H₁₂ + 8O₂ → 5CO₂ + 6H₂O

1- to solve the problem, we write:

C₅H₁₂ + 8O₂ → 5CO₂ + 6H₂O

72 g 8x32g

14.4g x

3- The consumed amount of oxygen=

X= 14.4g x 256 g/72 g = 51.2 g

4- the remainin amount of oxygen=

100 – 51.2 = 48.8 g

b-when 0.20 mol of magnisum Mg is reacted with excess of nitrogen, how many moles of nitrogen are consumed?

3Mg + N₂ → Mg₃N₂

c- what mass of NaOH, in grams is required to prepare 120 ml of 0.20 M of NaOH solution?

d- Calcium oxide reacts with carbon dioxide to form calcium carbonate :

CaO(s) + CO₂(g) → CaCO₃(s) ΔH= - 178.4 kJ

What is the heat evolved in the formation of 500 g of CaCO₃ ?

e-use the following equations:N₂(g) + 2O₂(g) → N₂O₂(g) ΔH=9.2 kJN₂(g) + 2O₂(g) → 2NO₂(g) ΔH=33.2 kJto calculate the enthalpy change for the reaction:2NO₂(g) → N₂O₄(g) ΔH=?

f-write the electron configuration for copper Cu (Z=29) using both : spdf notation and orbital diagram, then the noble gas abbreviation.

g- use the lewis theory to show the ionic bond of Ca & Cl .

h- write the resonance structures of SO₂ accourding to Lewis's theory, the show the formal charge of each atom.

i- how would you prepare 500 ml of an aqueous solution that is 3.0 % KOH by mass.

j- what is the concentration in ppm of 0.40 g of NO₃ˉ in one litter of water.

Answer:

1 ppm = 1 mg/liter

The number of ppm ( miligrams ) per liter=

0.40x1000= 400 ppm

k-what is the molality of sodium chloride NaCl in a solution containing 117 g of this salt in 360 ml of water.

Answer :

Molality = the number of moles of the solute/the mass of the solvent in Kg

1- the molar mass of NaCl = 23 + 35.5 = 58.5 g

2- the number of moles ( NaCl) = 117/58.5 =2 mol

3- the mass of the solvent( H₂O)=360g = 0.360 Kg

4- the molality= 2/0.360=

l-Arrange the following in order of increasing the first ionization energy:

C , N, F , O , Be

m-Arrange the following in order of increasing the electronegativity:

O, AS , P

Q4- Define the following terms:(answer only four)

(a) Nonmetals

(b) Ionic Bond

(c) Molecule

(d) Electron Affinity

(e) Standard Enthalpy of Formation

GOOD LUCK