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Equilibrium

Multiple Choice Questions

41.
In which of the following mixed aqueous solutions, pH =pK_aat equilibrium?
(1) 100 mL of 0.1 M CH₃COOH +100mL 0.1 M CH₃COONa.
(2) 100 mL of 0.1 M CH₃COOH + 50 mL of 0.1 M NaOH.
(3) 100 mL of 0.1 M CH₃COOH + 100 mL of 0.1 M NaOH.
(4) 100 mL of 0.1 M CH₃COOH + 100 mL of 0.1 M NH_3.

(1) is correct

(2) is correct

(3) is correct

Both (1) and (2) are correct

(1) is correct

(2) is correct

Both (1) and (2) are correct

$pH of buffer solutions is given by pH = {pK}_{a} + \log \frac{[salt]}{[acid]} (1) {CH}_{3} COOH and {CH}_{3} COONa 100 \times 0.1 100 \times 0.1 No . of milimoles = 10 = 10 \cdot : [salt] = [acid] = 10, pH = {pK}_{a} + \log \frac{10}{10} pH = {pK}_{a} (2) \underset{100 \times 0.1}{{CH}_{3} COOH} + \underset{50 \times 0.1}{NaOH} \to {CH}_{3} COONa + H_{2} O Initial = 10 5 0 0 Final = 5 0 5 0 [salt] = [acid] = 5, pH = {pK}_{a} + \log \frac{5}{5} therefore pH = {pK}_{a} (3) \underset{100 \times 0.1}{{CH}_{3} COOH} + \underset{50 \times 0.1}{NaOH} \to {CH}_{3} COONa + H_{2} O Initial = 10 10 0 0 Final = 0 0 10 10 [salt] = 10 and [acid] = 0 pH = {pK}_{a} + \log \frac{10}{0} therefore pH = {pK}_{a} (4) {CH}_{3} COOH + {NH}_{3} \to {CH}_{3} {COONH}_{4} Initial = 10 10 \to No buffer action Final due to weak {CH}_{3} {COONH}_{4} salt pH \neq {pK}_{a}$

42.

Consider the following salts : NaCl, HgCl₂, Hg₂Cl₂, CuCl₂, CuCl and AgCl.

Identify the correct set of insoluble salts in water.

Hg₂Cl₂, CuCl, AgCl
HgCl₂, CuCl_, AgCl
Hg₂Cl₂, CuCl₂, AgCl
Hg₂Cl₂, CuCl, NaCl

43.

The ratio of volumes of CH₃COOH 0.1 N to CH₃COONa 0.1 N required to prepare a buffer solution of pH 5.74 is (Given, pK_a of CH₃COOH is 4.74)

10 : 1
5 : 1
1 : 5
1 : 10

44.

Within the list shown below, the correct pair of structures of alanine in pH ranges 2-4 and 9-11 is

I. H₃N⁺- CH(CH₃)CO₂H

II. H₂N - CH(CH₃)CO $_{2}^{-}$

III. H₃N⁺-CH(CH₃)CO $_{2}^{-}$

IV. H₂N-CH(CH₃)CO₂H

I and II
I and III
II and III
III and IV

45.

The correct statement regarding the following energy diagrams is

Reaction M is faster and less exothermic than reaction N
Reaction M is slower and less exothermic than reaction N
Reaction M is faster and more exothermic than reaction N
Reaction M is slower and more exothermic than reaction N

46.

At 25°C, the solubility product of salt of MX₂ type is 3.2 × 10^-8 in water. The solubility (in mol/L) of MX₂ in water at the same temperature will be

1.2 × 10^-3
2 × 10^-3
3.2 × 10^-3
1.75 × 10^-3

47.

The different colours of litmus in acidic, neutral and basic solutions are, respectively.

red, orange and blue
blue, violet and red
red, colourless and blue
red, violet and blue

48.

The correct order of equivalent conductances at infinite dilution in water at room temperature for H⁺, K⁺, CH₃COO^- and HO^- ions is

HO^- > H⁺ > K⁺ > CH₃COO^-
H⁺ > HO^- > K⁺ > CH₃COO^-
H⁺ > K⁺ > HO^- > CH₃COO^-
H⁺ > K⁺ > CH₃COO^- > HO^-

49.

The pH of 10^-4 M KOH solution will be

4
11
10.5
10

50.

For a chemical reaction at 27°C, the activation energy is 600 R. The ratio of the rate constants at 327°C to that of at 27°C will be