Salt of Weak Acid and Weak Base

Q. The ionization constant of ammonium hydroxide is $1.77\times {10}^{-5}$ at $298K$. Hydrolysis constant of ammonium chloride is:

1. $5.56\times {10}^{-12}$
2. $5.65\times {10}^{-10}$
3. $6.50\times {10}^{-12}$
4. $5.65\times {10}^{-13}$

Q. When 10 mL of 0.1 M acetic acid $(p{K}_a=5.0)$ is titrated against 10 mL of 0.1 M ammonia solution $(p{K}_b=5.0)$ the equivalence point occurs at pH of:

1. 5
2. 6
3. 7
4. 9

Q.

Calculate the degree of hydrolysis ammonium acetate. Given $K_a$ = $1.75\times {10}^{-5}$ ; $K_b$ = $1.80\times {10}^{-5}$.

1. 

2. 

3. 

4. 

Q. The dissociation constants for aniline, acetic acid and water at ${25}^{\circ }\text{C}$ are $4\times {10}^{-10},2\times {10}^{-5}$ and ${10}^{-14}$ respectively. Calculate degree of hydrolysis of aniline acetate in a decinormal solution.

1. 0.15
2. 0.45
3. 0.53
4. 0.35

Q. Which of the following describes the correct relation for hydrolysis constant $\left(K_h\right)$ for a salt of weak acid and weak base at ${25}^{\circ }C?$

1. $K_h=\frac{K_w}{K_a\times K_b}$
2. $K_h=\frac{K_a}{K_w\times K_b}$
3. $K_h=\frac{K_a\times K_b}{K_w}$
4. $K_b=\frac{K_h}{K_a\times K_w}$

Q.

$15\mathrm{mL}$ of an aqueous solution of ${\mathrm{Fe}}^{+2}$ in the acidic medium completely reacted with $20\mathrm{mL}$ of $0.03\mathrm{M}$ aqueous $C{r}_2{O_7}^{-2}$. The molarity of ${\mathrm{Fe}}^{+2}$ solution is $\mathrm{\_\_\_\_\_\_}\mathrm{x}{10}^{-2}\mathrm{M}$.(Round off to the Nearest Integer).

Q. Calculate the degree of hydrolysis $\left(h\right)$ of a salt of aniline and acetic acid in 0.1 M solution at ${25}^{\circ }C$
Given :
$K_a$ for $C{H}_{3}COOH$ is $1.8\times {10}^{-5}$
$K_b$ for aniline is $4.6\times {10}^{-10}$

1. 0.996
2. 0.85
3. 0.235
4. 0.523

Q. Which of the following statement(s) is/are correct for a salt of weak acid and weak base in an aqueous solution at ${25}^{\circ }C$.

Here, $K_a$ is the dissociation constant for a weak acid and $K_b$ is the dissociation constant for a weak base.

1. If $K_a>K_b$ then the solution is neutral.
2. If $K_a<K_b$ then the solution is acidic in nature.
3. If $K_a>K_b$ then the solution is acidic in nature.
4. If $K_a<K_b$ then the solution is alkaline in nature.

Q. $p{k}_a$ of acetic acid and $p{K}_b$ of ammonium hydroxide are 4.76 and 4.75 respectively. Calculate the pH of ammonium acetate solution.

1. $6.02$
2. $7.005$
3. $8$
4. $5.602$

Q. In order to prepare a buffer solution of pH 5.74, sodium acetate is added to acetic acid. If the concentration of acetic acid in the buffer is 1.0 M, the concentration of sodium acetate in the buffer is ______M. (Round off to the Nearest Integer).
[Given: $p{K}_a$ (acetic acid) = 4.74]

Q. $\text{pOH}=7–0.5p{K}_a+0.5p{K}_b$ is true for an aqueous solution that has which pair of cations and anions amongst the following?

1. $C_6{H}_{5}N{H}_3^{+},C{H}_{3}CO{O}^{-}$
2. $N{H}_4^{+},F^{-}$
3. $N{a}^{+},C{H}_{3}CO{O}^{-}$
4. $N{H}_4^{+},C{l}^{-}$

Q. Ammonium acetate which is 0.01 M, is hydrolysed to 0.001 M concentration. Calculate the change in pH in 0.001 M solution, if initially $pH=p{K}_a.$
$log9=0.354,log3=0.477$

1. -1
2. 1
3. 2
4. -2

Q. Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion: Nitrating mixture used for carrying our nitration of benzene consists of $conc.HN{O}_3+conc.H_{2}S{O}_4.$

Reason :In presence of$H_{2}S{O}_4,HN{O}_3$ acts as a base and produces$N{O}_2^{+}$ions.

1. If both assertion and reason are true and the reason is the correct explanation of the assertion.
2. If assertion is true but reason is false.
3. If the assertion and reason both are false.
4. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Q. Which of the following describes the correct relation for $pOH$ for an aqueous salt solution of weak acid and weak base at ${25}^{\circ }C?$

1. $pOH=14-\frac{1}{2}(p{K}_a-p{K}_b)$
2. $pOH=7+\frac{1}{2}(p{K}_a-p{K}_b)$
3. $pOH=7-\frac{1}{2}(p{K}_a-p{K}_b)$
4. $pOH=14+\frac{1}{2}(p{K}_a-p{K}_b)$

Q.
Relation between above compounds is:

1. Position isomers
2. Chain isomers
3. Identical
4. Functional isomers

Q. When 10 mL of 0.1 M acetic acid $(p{K}_a=5.0)$ is titrated against 10 mL of 0.1 M ammonia solution $(p{K}_b=5.0)$ the equivalence point occurs at pH of:

1. 5
2. 6
3. 7
4. 9

Q. Which of the following statement is correct regarding an eqiumolar solution of a weak acid $C{H}_{3}COOH$ and a weak base $N{H}_{4}OH$ at ${25}^{\circ }C$ ?

1. Higher the concentration of $C{H}_{3}COOH$, lesser is the $pH$ value.
2. Higher the concentration of $N{H}_{4}OH$, higher is the $pH$ value.
3. $pH$ does not depend on the concentration of $C{H}_{3}COON{H}_4$.
4. None of the above

Q. When $10mL$ of $0.1M$ acetic acid ($p{K}_a=5.0$) is titrated against $10mL$ of $0.1M$ ammonia solution $(p{K}_b=5.0)$, the equivalence point occurs at pH:

1. $9.0$
2. $6.0$
3. $7.0$
4. $5.0$

Q. $p{K}_a$ of a weak acid $\left(HA\right)$ and $p{K}_b$ of a weak base $\left(BOH\right)$ are $3.2$ and $3.4$, respectively. The $pH$ of their salt $\left(AB\right)$ solution is :

1. $7.0$
2. $7.2$
3. $1.0$
4. $6.9$

Q. $5.0mL$ of $0.1MNaOH$ solution is added to $50mL$ of the $0.1M$ acetic acid solution. Calculate the $pH$ of the resulting acetic acid solution.

Q. In a solution of $NaHC{O}_3$ , in amphiprotic anion can undergo ionization to form $H^{+}$ ion and hydrolysis to form $O{H}^{-}$ ion.
$HC{O}_3^{-}+H_{2}O\stackrel{ionization}{\leftrightharpoons }C{O}_3^{2-}+H_3{O}^{+}$
$HC{O}_3^{-}+H_{2}O\stackrel{hydrolysis}{\leftrightharpoons }{H}_{2}C{O}_3^{-}+O{H}^{-}$ to calculate pH, suitable approximation is :

1. $\left[C{O}_3^{2-}\right]=\left[H_{2}C{O}_3\right]$
2. neither 'A' nore 'B'
3. Degree of ionization = degree of hydrolysis
4. both (A) and (B)

Q. Match the column I with column II and mark the appropriate choice.

Column I	Column II
(A) $C{H}_{3}COONa$	(i) Almost neutral, pH > $7$ or < $7$
(B) $N{H}_{4}Cl$	(ii) Acidic, pH < $7$
(C) $NaN{O}_3$	(iii) Alkaline, pH > $7$
(D) $C{H}_{3}COON{H}_4$	(iv) Neutral, pH = $7$

1. (A) - (i) ; (B) - (ii) ; (C) - (iii) ; (D) - (iv)
2. (A) - (iii) ; (B) - (ii) ; (C) - (iv) ; (D) - (i)
3. (A) - (ii) ; (B) - (iii) ; (C) - (iv) ; (D) - (i)
4. (A) - (iv) ; (B) - (i) ; (C) - (iii) ; (D) - (ii)

Q.
If the molecular formula of compound E is $C_x{H}_y{O}_z$. Then, the value of $y-x-z$ is:

Q. The dissociation constants for aniline, acetic acid and water at ${25}^{\circ }\text{C}$ are $4\times {10}^{-10},2\times {10}^{-5}$ and ${10}^{-14}$ respectively. Calculate degree of hydrolysis of aniline acetate in a decinormal solution.

1. 0.53
2. 0.15
3. 0.35
4. 0.45

Q. Which of the following statement is correct regarding an eqiumolar solution of a weak acid $C{H}_{3}COOH$ and a weak base $N{H}_{4}OH$ at ${25}^{\circ }C$ ?

1. Higher the concentration of $C{H}_{3}COOH$, lesser is the $pH$ value.
2. Higher the concentration of $N{H}_{4}OH$, higher is the $pH$ value.
3. $pH$ does not depend on the concentration of $C{H}_{3}COON{H}_4$.
4. None of the above

Q. What will be the $pH$ of an aqueous solution of $1.0M$ ammonium formate?

1. $7.5$
2. $3.4$
3. $6.5$
4. $10.2$

Q. What will be the $pH$ of $0.1M$ ${CH}_{3}COO{NH}_4$? Dissociation constants of ${CH}_{3}COOH$ and ${NH}_{4}OH$ are $K_a=1.8\times {10}^{-5}$ and $K_b=1.8\times {10}^{-5}$ respectively.

Q. The ratio of volumes of $C{H}_{3}COOH$ $\left(0.1N\right)$ to $C{H}_{3}COONa$ $\left(0.1N\right)$ required to prepare a buffer solution of $pH$ 5.74 is:

1. 1 : 5
2. 1 : 10
3. 10 : 1
4. 5 : 1

Q. The solution of a salt of a weak acid and weak base will have pH: ($K_b=1\times {10}^{-6}$ and $K_a=1\times {10}^{-4}$)

1. $7.0$
2. $8.0$
3. $6$
4. $4.0$

Q.

The degree of hydrolysis of ammonium acetate is related to its hydrolysis constant by the expression

1. $a$ = $\frac{Kh}{(1+Kh)}$

2. $a$ = $\frac{Kh}{(1+K{h}^2)}$

3. $a$ = $\frac{\sqrt{Kh}}{(1+\sqrt{Kh})}$

4. $a$ = $\sqrt{\frac{Kh}{(1+Kh)}}$