### Chemical Equilibrium and Acids - Bases

1. Kc for a reaction at 27°C and 127°C are 1.6 × 10-3 and 7.6 × 10-2 respectively. Hence the reacton is
1) exothermic

2) endothermic
3) upto 27°C exothermic above 127°C endothermic
4) upto 27° endothermic above 127°C exothermic
Ans: (2)
Explanation: Kc ∝ T. So it is endothermic.

2. The correct relation between reaction Quotient (Qc) and equilibrium constant (Kc) is
1) Qc > Kc for the reverse reaction

2) Qc < Kc for the forward reaction
3) Qc = Kc for the reaction at equilibrium

4) all are correct
Ans: (4)
Explanation: all are correct.

3. The equilibrium constant (Kc) for the reaction N2 (g) + O2 (g) 2 NO (g) at temperature T is 4 × 10-4. The value of Kc for the reaction NO (g) N2 (g) +  O2 (g) at the same temperature is
1) 0.02              2) 2.5 × 102           3) 4 × 10-4              4) 50
Ans: (4)
Explanation:

4. A vessel at 1000 K contains CO2 with a pressure of 0.5 atm. Some of the CO2 is converted into CO on the addition of graphite. If the total pressure at equilibrium is 0.8 atm, the value of Kp is
1) 1.8 atm                 2) 3 atm             3) 0.3 atm          4) 0.18 atm
Ans: (1)
Explanation:

5. If the total pressure at equilibrium of the following reaction is ‘p’ and the degree of dissociation of PCl5 is x, the partial pressure of PCl3 will be
PCl5  ⇌ PCl3 + Cl2

Ans: (3)
Explanation:

6. The equilibrium constant for the reaction SO3 (g) ⇌ SO2 (g) +  O2 (g) is
= 4.9 × 10-2. The value of  for the reaction 2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g) is
1) 4.9 × 10-2          2) 416           3) 2.4 × 10-3            4) 9.8 × 10-2
Ans: (2)
Explanation:

7. The dissociation constants K1 and K2 for acetic acid and HCN at 25°C are 1.5 × 10-5 and 4.5 × 10-10 respectively. The equilibrium constant Kc for the reaction
CN- + CH3COOH ⇌ HCN + CH3COO- would be approximately
1) 3 × 105         2) 3 × 10-4           3) 3 × 10-5          4) 3 × 104
Ans: (4)
Explanation:

8. Equimolar concentrations of H2 and I2 are heated to equilibrium in a 2 litre flask. At equilibrium, the forward and backward rate constants are found to be equal. What percentage of initial concentration of H2 has reacted at equilibrium?
1) 20%           2) 33%            3) 50%              4) 40%
Ans: (3)
Explanation:

The correct relationship for the above reaction is
1) K3 = K1K2          2) K1 = K2K3              3)                4)
Ans: (1)
Explanation:

10. If Hydrogen molecules decomposed into its atoms, the favourable conditions to give maximum yield of H atoms are
1) low T & high p       2) high T & low p

3) high T & high p      4) low T & low p
Ans: (2)
Explanation: H2 (g) ⇌ 2 H (g) —— Heat

11. If  ,  and  of phosphoric acid are 7.5 × 10-3, 6.2 × 10-8 and 4.2 × 10-13 respectively. Kc for the reaction H3PO4 ⇌ 3 H+ + PO4 -3 is
1) 7.5 × 10-3                 2) 4.7 × 10-17

3) 4.2 × 10-13                 4) 1.95 × 10-22
Ans: (4)
Explanation: Kc =  .  .  = 7.5 × 10-3 × 6.2 × 10-8 × 4.2 × 10-13
= 1.95 ×10-22

12. Kp/ Kc for the reaction CO (g) + Cl2 (g) ⇌ COCl2 (g) will be
1) RT               2) (RT)1/2              3) (RT)-1            4) 1.0
Ans: (3)
Explanation:

13. If 33.33% of HI decomposes at a temperature T, Kc for the reaction 2 HI ⇌ H2 + I2 will be
1) 0.5           2) 0.25            3) 1.7 × 10-1              4) 6.25 × 10-2
Ans: (4)
Explanation:

14. For the reaction N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g) the ratio of Kp and Kc at 1218 K is
[R = 0.0821 L atm mol-1 K-1]
1) 104              2) 106              3) 10-4           4) 10-6
Ans: (3)
Explanation:

15. 56 g of N2 and 6 g of H2 were kept at 673 K in one litre vessel. The equilibrium mixture contained 27.54 g of NH3. The approximate value of Kc for this reaction will be
1) 6            2) 12               3) 24              4) 36
Ans: (2)
Explanation:

Acids - Bases

16. The pH of a 0.1 molar solution of the acid HQ is 3. The value of the ionizatin constant Ka of the acid is
1) 1 × 10-5              2) 1 × 10-3            3) 1 × 10-7               4) 3 × 10-1
Ans: (1)
Explanation:

17. The Ksp for Cr(OH)3 is 1.6 × 10-30. The molar solubility of this compound in water is

Ans: (3)
Explanation:

18. If the solubility product constant Ksp of AgIO3 at a given temperature is 1.0 × 10-8, the mass of AgIO3 present in 100 mI of its saturated solution is
1) 2.83 × 10-3 g         2) 2.83 × 10-2 g

3) 1 × 10-7 g              4) 1 × 10-4 g
Ans: (1)
Explanation:

19. NH3 can acts as
1) Lewis base           2) Bronsted base

3) Bronsted acid        4) all the above
Ans: (4)
Explanation: NH3 is Lewis base (electron pair donor), Bronsted base (proton donor) and Bronsted acid (proton acceptor).

20. Nature of aqueous CuSO4 solution is
1) basic            2) acidic           3) neutral           4) amphoteric
Ans: (2)
Explanation: CuSO4 is made of weak base & strong acid. So Cu+2 is strong acid, can undergo cationic hydrolysis to give H+ ions.
Cu+2 + 2 H2O Cu(OH)2 + 2 H+

21. The correct order of ionisation constants for orthophosphoric acid is

Ans: (1)
Explanation:

It is more difficult to remove a proton from HPO4-2 compared to H2PO4- and H3PO4.

22. Sealed water bottle on opening show the evolution of gas with effervescence, because
1) difference in solubility of CO2 at different pressures.
2) sealed soda bottle on opening shows evolution of gas with effervescence.
3) equilibrium between gaseous molecules and dissolved molecules (liquid state).
4) all the statements are correct.
Ans: (4)
Explanation: all are correct.

23. The ratio of dissociated water to that of undissociated water is
1) 1 × 10-7              2) 1.8 × 10-9            3) 1 × 10-14           4) 1.8 × 10-7
Ans: (2)
Explanation:

24. The pka of CH3COOH and pkb of NH4OH are 4.76 and 4.75 respectively. The pH of ammonium acetate is
1) 0              2) 4.76              3) 7.005           4) 4.75
Ans: (3)
Explanation:

25. pH of saturated solution of NaOH is
1) 13              2) 14            3) 0           4) > 15
Ans: (4)
Explanation: As concentration of saturated NaOH solution high. Usally pH is 15.1 to 15.5.

26. pH values of 10-8 M HCl and 10-8 M NaOH are respectively
1) 8 & 8              2) 8 & 6            3) 6.96 & 7.04            4) 6 & 8
Ans: (3)
Explanation: For 10-8 M HCl: [H+] = 10-7 + 10-8 = 1.1 × 10-7 ∴ pH = 6.96
For 10-8 M NaOH: [OH-] = 10-7 + 10-8 = 1.1 × 10-7 ∴ pOH = 6.96
∴ pH = 14 - pOH = 14 - 6.96 = 7.04

27. Which of the following order is true with respect to acidic nature?
a) HF < HCl < HBr < HI         b) CH4 < NH3 < H2O < HF
1) a only correct            2) b only correct

3) a & b are wrong      4) both a and b are correct
Ans: (4)
Explanation:

28. Solubility of Zirconium phosphate is
1) 27 S3            2) 6912 S7              3) 4 S3           4) 108 S4
Ans: (2)
Explanation: (Zr)3(PO4) 3 Zr+4         +          4 PO4 -3
3S                             4S
Ksp = (3S)3(4S)4

29. The Ksp values of two sparingly soluble salts Ni(OH)2 and AgCN are 2 × 10-15 and 6 × 10-17 respectively. The more soluble salt is
1) AgCN                                 2) Ni(OH)2

3) both are equally soluble     4) both are insoluble
Ans: (2)
Explanation: For AgCN, Ksp = [S1][S1] = 6 × 10-17 ∴ S1 = 7.8 × 10-9
For Ni(OH)2, Ksp = [S2][2S2]2 = 4S23 ∴ S2 = 0.58 × 10-4
S2 > S1 ∴ Ni(OH)2 is more soluble than AgCN.

30. The volume (in ml) of 0.1 M sodium formate solution should be added to 50 ml of 0.05 M formic acid to produce a buffer solution of pH = 4.0 is (pka of formic acid = 3.8)
1) 39.62 ml           2) 93.62 ml            3) 36.29 ml          4) 26.39 ml
Ans: (1)
Explanation:

Posted Date : 15-10-2020