The Islamic University of Gaza

The Islamic University of Gaza

/ /

Chemistry Department

General Chemistry B.(CHEMB 1301) / Time:2 hours / 50
اسم الطالب...... الرقم الجامعي ...... اسم المدرس......

R = 8.314 J/mol.K, or = 0.0821 L.atm/mol.K

Answer All Questions:

1- Balance the following equation in acidic solution and determine the coefficient of H+ and its location (right or left

side) in the equation.

I2 + ClO4-  IO3- + ClO3-

a. 4, right b. 2, right c. 6, right d. 4, left

2- An electrochemical cell based on the following reaction has a standard cell voltage (Eocell) of 0.48 V.

Sn(s) + Cu2+(aq)  Sn2+(aq) + Cu(s)

Given: Eo Cu2+/Cu = +0.34 V, what is the Eo Sn2+/Sn

a. ─ 0.14 V b. 0.14 V c. ─ 0.82 V d. 0.82 V

3- If the measured voltage of the following cell Zn(s) | Zn2+(aq) || Ag+(aq) | Ag(s) is 1.37 V when the concentration of Zn2+ ion is 0.010 M, then what is the Ag+ ion concentration?

Given: Eo Ag+/Ag = 0.80 V , Eo Zn2+/Zn = - 0.76 V

a. 6.1  10 ─ 5 M b. 4.0  10 ─ 9 M c. 4.0  10 ─ 9 M d. 2.5 M

4- Determine the value of the equilibrium constant (Keq) at 25oC for the reaction:

Cl2(g) + 2Br ─ (aq) D 2Cl ─ (aq) + Br2(l)

Given: Eo Br2(l)/Br- = 1.07 V , Eo Cl2(g)/Cl- = 1.36 V

a. 6.3  109 b. 1.5  10 ─ 10 c. 1.3  1041 d. 8.1  104

5- A reaction is spontaneous at high temperatures if

a. ΔH and ΔS are both positive. b. ΔH and ΔS are both negative.

c. ΔH is positive and ΔS is negative. d. ΔH is negative and ΔS is positive.

6- The equilibrium constant for the reaction: AgBr(s) D Ag+(aq) + Br-─(aq) is Ksp = 7.7  10 ─ 13 at 25oC.

Calculate ΔG for the reaction when [Ag+] = 1.0  10-2 M and [Br-─] = 1.0  10 ─ 3 M. Is the reaction

spontaneous or nonspontaneous at these concentrations?

a. ΔG = 69.1 kJ, nonspontaneous b. ΔG = ─69.1 kJ, spontaneous

c. ΔG = 97.5 kJ, spontaneous d. ΔG = 40.6 kJ, nonspontaneous

7- Nitrosyl chloride (NOCl) decomposes at elevated temperatures according to the equation.

2NOCl(g) D 2NO(g) + Cl2(g)

Use the following information to calculate Kp for this reaction at 227oC.

ΔHo = 81.2 kJ ΔSo = 128 J/K

a. 1.60  10 ─ 2 b. 2.1  10 ─ 7 c. 62.8 d. 4.9  106

8- Arrange the following compounds in order of increasing standard molar entropy at 25oC:

C3H8(g), C2H4(g), ZnS(s), and H2O(l).

a. ZnS(s) < H2O(l) < C3H8(g) < C2H4(g)

b. C2H4(g) < H2O(l) < C3H8(g) < NaCl(s)

c. ZnS(s) < C3H8(g) < C2H4(g) < H2O(l)

d. ZnS(s) < H2O(l) < C2H4(g) < C3H8(g)

9- The solubility of BaCrO4 (formula weight = 253.3) is 3.5 x10-3 g/L. What is the Ksp?

a. 3.0 x 10-8 b. 1.9 x 10-10 c. 1.4 x 10-5 d. 1.9 x 10-5

10- What is the pH of a saturated solution of Mg(OH)2 (Ksp = 1.8 x 10-11)?

a. 11.43 b. 10.52 c. 11.73 d. 12.01

11- What is the pH of a solution of 0.17 M acid and 0.50 M of its conjugate base, if the Ka is 2.87 x 10-9?

a. 9.01 b. 9.71 c. 9.98 d. 9.59

12- What is the pH of a 0.68 M CN- solution? (Ka of HCN = 4.4 x 10-10)

a. 10.80 b. 11.60 c. 11.10 d. 10.60

13- A 25.00 mL sample of 0.100 M CH3COOH is titrated with 0.100 M NaOH. What is the pH of the

solution at the points where 24.5 and 25.5 mL of NaOH have been added. (Ka = 1.8 x 10-5)

a. 6.43, 11.00 b. 7.00, 8.00 c. 6.13, 9.85 d. 6.44, 9.85

14- Hydrosulfuric acid (H2S) has K1 = 1.1 x 10-7 and K2 = 1.0 x 10-13. What is the H+ ion concentration of

a 0.10 M solution of H2S?

a. 1.0 x 10-4 b. 1.1 x 10-7 c. 3.3 x 10-5 d. 3.3 x 10-4

15- What is the ionization constant of HA if the H+ ion concentration of a 0.390 M solution is 4.52 x 10-5 M?

a. 5.24 x 10-9 b. 7.94 x 10-10 c. 4.52 x 10-4 d. 1.02 x 10-9

16- Consider the following salts. Which one(s) when dissolved in water will produce a basic solution?

1) NaNO3, 2) CH3COONa, 3) Na2CO3

a. 2 and 3 b. only 3 c. 1 and 2 d. only 2

17- What is the conjugate acid of methylamine, CH3NH2?

a. CH3NH- b. CH3NH3+ c. CH3NH2+ d. CH3NH+ -

18- The Ka values for HS- and HPO42- are 1.2 x 10-13 and 4.8 x 10-13 respectively. Therefore it follows the HS- is

a _____ acid than HPO42- and S2- is a _____ base than PO43-.

a. weaker, weaker b. stronger, stronger

c. stronger, weaker d. weaker, stronger

19- Consider the reactions below. In which cases is product formation favored by increased temperature?

1) CO(g) + 3 H2(g) D CH4(g) + H2O(g) Ho = -206.2 kJ

2) CO2(g) + C(s) D 2 CO(g) Ho = 172.5 kJ

3) H2(g) + I2(g) D 2 HI(g) Ho = -9.4 kJ

4) 3 O2(g) D 2 O3(g) Ho = 285 kJ

5) 2 H2O(g) D 2 H2(g) + O2(g) Ho = 484.6 kJ

a. 1, 3 b. 2, 4, 5 c. 1, 4 d. 3, 5

20- Consider the following reactions at equilibrium and determine which of the indicated changes will cause the

reaction to proceed to the right.

1) CO(g) + 3 H2(g) D CH4(g) + H2O(g) (remove H2O)

2) N2(g) + 3 H2(g) D 2 NH3(g) (add NH3)

3) H2(g) + F2(g) D 2 HF(g) (add HF)

4) N2(g) + 2 O2(g) D 2 NO2(g) (add N2)

5) BaO(s) + SO3(g) D BaSO4(s) (add BaO)

a. 2, 3 b. 3, 5 c. 1, 4 d. 1, 4, 5

21- The equilibrium constant for the following reaction is 0.28 at 900oC. A system at equilibrium has

[H2S] = 0.100 M, [H2] = 0.100 and [CH4] = 1.40 x 10-4 M. What is the [CS2]?

CS2(g) + 4 H2(g) D CH4(g) + 2 H2S(g)

a. 0.25 b. 0.15 c. 0.10 d. 0.050

22- The equilibrium constant Kc for the following reaction at 227oC is 10.5 x 10-2. What is Kp at this temperature?

CO(g) +2 H2(g) D CH3OH(g)

a. 6.23 x 10-5 b. 1.76 x 104 c. 2.56 x 10-1 d. 177

23- At 35oC and 70oC the first order rate constants of a reaction are 2.50 x 10-5 and 3.26 x 10-3 s-1 respectively. What is the enthalpy of activation (kJ/mole)?).

a. 117 b. 127 c. 122 d. 130

24- A 12.0 g sample of a nonelectrolyte is dissolved in 80.0 g of water. The solution freezes at -1.94oC. What is the molecular weight of the substance? (Kf = -1.86oC/m).

a. 162 b. 144 c. 156 d. 136

25- Which of the following liquids should have the highest viscosity at the same temperature?

a. CH3OCH3 b. CH2Cl2 c. C2H5OH d. HOCH2CH2OH

Good Luck

1