The ionization constant  of $\left[{\mathrm{NH}}_4^{+}\right]$ in water is $5.6\times {10}^{-10}$ at $25°\mathrm{C}$. The rate constant for the reaction of $\left[{\mathrm{NH}}_4^{+}\right]$ and $\left[{\mathrm{OH}}^{-}\right]$ to form NH₃ and H₂O is $3.4\times {10}^{10} \mathrm{lit} {\mathrm{mol}}^{-1 }{\sec }^{-1}$ at $25°\mathrm{C}$. The rate constant for the proton transfer from water to NH₃ in $\mathrm{lit} {\mathrm{mol}}^{-1} {\sec }^{-1}$ is

1. $6.07\times {10}^5$

2. $6.07\times {10}^{-5}$

3. $6.07\times {10}^{-3}$

4. $6.07\times {10}^{-4}$

The equilibrium constant of ${\mathrm{NH}}_4^{+}$ to NH₃ and H⁺ is 10^-10. The rate constant for ${\mathrm{NH}}_4^{+}+{\mathrm{OH}}^{-}\to {\mathrm{NH}}_3+{\mathrm{H}}_2\mathrm{O}$ is 10¹⁰. The rate constant for ${\mathrm{NH}}_3+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{NH}}_4^{+}+{\mathrm{OH}}^{-}$ is:

1. ${10}^5$

2. ${10}^{20}$

3. ${10}^8$

4. ${10}^9$

An acid base indicator has ${\mathrm{K}}_{\mathrm{a}}=3\times {10}^{-5}$. The acid form of the indicator is red and the basic form is blue. By how much must the pH change in order to change the indicator from 75% red to 75% blue (log 3=0.4770)

1. 0.95

2. 2.3

3. 0.75

4. 5

The dissociation constants for aniline, acetic acid and ionic product of water at $25°\mathrm{C}$ are $3.83\times {10}^{-10}, 1.75\times {10}^{-5} \mathrm{and} 1.008\times {10}^{-14}$ respectively. The degree of hydrolysis of aniline acetate in a decinormal solution is

1. 0.56%

2. 55%

3. 5.6%

4. 2.75%

A solution of benzoic acid (a weak monobasic acid) is titrated with NaOH. The pH of the solution is 4.2 when half of the acid is neutralized. The dissociation constant of the acid will be:

1. $3.2\times {10}^{-5}$

2. $6.42\times {10}^{-4}$

3. $6.31\times {10}^{-5}$

4. $8.7\times {10}^{-8}$

The mixture that shows the maximum buffer capacity is:

1. $0.1 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}+0.2 \mathrm{M}\hspace{0.17em}{\mathrm{CH}}_3\mathrm{COONa}$

2. $0.1 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}+0.15 \mathrm{M}\hspace{0.17em}{\mathrm{CH}}_3\mathrm{COONa}$

3. $0.05 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}+0.15 \mathrm{M}\hspace{0.17em}{\mathrm{CH}}_3\mathrm{COONa}$

4. $0.1 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}+0.12 \mathrm{M}\hspace{0.17em}{\mathrm{CH}}_3\mathrm{COONa}$

The pH of a solution containing 0.1 mol of CH₃COOH, 0.2 mol of CH₃COONa, and 0.05 mol of NaOH in 1 L of solution is-

(pK_a of CH₃COOH=4.74 and log 5=0.7)

1. 4.56

2. 5.44

3. 5.04

4. 3.74

18 ml of mixture of acetic acid and sodium acetate required 6 ml of 0.1 M NaOH for neutralization of the acid and 12 ml of 0.1 M HCl for reaction with salt separately. If pK_a of the acid is 4.75, what is the pH of the mixture?

1. 5.05

2. 4.75

3. 4.5

4. 4.6

What is the minimum pH required to prevent the precipitation of ZnS in a solution that is 0.01 M ZnCl₂ and saturated with 0.10 M H₂S?

$[\mathrm{Given} : {\mathrm{K}}_{\mathrm{sp}} \mathrm{of} \mathrm{ZnS}={10}^{-21}, {\mathrm{K}}_{{\mathrm{a}}_1}\times {\mathrm{K}}_{{\mathrm{a}}_2} \mathrm{of} {\mathrm{H}}_2\mathrm{S}={10}^{-20}]$

1. 4

2. 3

3. 2

4. 1

Which of the following is an amphiprotic (can accept and give protons) ion?

1. ${\mathrm{HPO}}_3^{-}$

2. ${\mathrm{H}}_2{\mathrm{PO}}_2^{-}$

3. ${\mathrm{H}}_3{\mathrm{PO}}_4$

4. ${\mathrm{H}}_2{\mathrm{PO}}_4^{-}$