Conjugate Acids and Bases

Q. Which one of the following is not a conjugate acid-base pair?

1. $HN{O}_2,N{O}_2^{-}$
2. $C{H}_{3}N{H}_3^{+},C{H}_{3}N{H}_2$
3. $H_3{O}^{+},O{H}^{-}$
4. $C_6{H}_{5}COOH,C_6{H}_{5}CO{O}^{-}$

Q. Conjugate base of $HC{O}_3^{-}$ in the given is:
Reaction :$HC{O}_3^{-}+H_{2}O\to C{O}_3^{2-}+H_3{O}^{+}$

1. $H_3{O}^{+}$
2. $H_{2}C{O}_3$
3. $C{O}_3^{2-}$
4. $H_{2}O$

Q. The order of increasing acidic strength of $C{H}_4,N{H}_3,H_{2}O,HF$ is :

1. $C{H}_4<N{H}_3<H_{2}O<HF$
2. $HF<N{H}_3<H_{2}O<C{H}_4$
3. $HF<C{H}_4<H_{2}O<N{H}_3$
4. $N{H}_3<H_{2}O<C{H}_4<HF$

Q. The strongest conjugate base is :

1. $N{O}_3^{-}$
2. $C{l}^{-}$
3. $C{H}_{3}CO{O}^{-}$
4. $S{O}_4^{2-}$

Q.

What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species:
$HN{O}_2,C{N}^{-},HCl{O}_4,F^{-},O{H}^{-},C{O}_3^{2-}$, and $S^{-2}$

Q. Conjugate base of $HC{O}_3^{-}$ is:

1. $H_{2}C{O}_3$
2. $C{O}_2$
3. $H_{2}O$
4. $C{O}_3^{2-}$

Q. Among the following, the species that act as the weakest base is:

1. $C{H}_3^{-}$
2. $C{H}_3{O}^{-}$
3. $C{l}^{-}$
4. $O{H}^{-}$

Q. Conjugate base of HCl is –

1. 
2. 
3. 
4. 

Q. $50\text{mL}$ of $0.1\text{M}N{a}_{3}P{O}_4$ was titrated with $50\text{mL}$ of $0.2\text{M}HCl$. Find the $pH$ of resulting mixture where $P{K}_{a_1},p{K}_{a_2}$ and $p{K}_{a_3}$ of $H_{3}P{O}_4$ are $5,8,13$:

Q. Assuming complete ionization, the pH of $0.1MHCl$ is 1. The molarity of $H_{2}S{O}_4$ with the same pH is :

1. 0.1
2. 0.2
3. 0.05
4. 2

Q. How much water must be added to $300\text{mL}$ of $0.2\text{M}$ solution of $C{H}_{3}COOH(K_a=1.8\times {10}^{-5})$ for the degree of ionisation $\left(\alpha \right)$ of the acid to double?

1. $600\text{mL}$
2. $900\text{mL}$
3. $1200\text{mL}$
4. $1500\text{mL}$

Q. Which one of the following can be classified as a Bronsted base:

1. $H_3{O}^{+}$
2. $N{H}_4^{+}$
3. $HCl$
4. $N{O}_3^{-}$

Q. Conjugate base of $N{H}_3$ is:

1. $N{H}_4^{+}$
2. $N{H}_2^{+}$
3. $N{H}_2^{-}$
4. $N_2$

Q. The order of increasing acidic strength of $C{H}_4,N{H}_3,H_{2}O,HF$ is :

1. $C{H}_4<N{H}_3<H_{2}O<HF$
2. $HF<N{H}_3<H_{2}O<C{H}_4$
3. $HF<C{H}_4<H_{2}O<N{H}_3$
4. $N{H}_3<H_{2}O<C{H}_4<HF$

Q. Conjugate base of Hydrazoic acid is

1. $H{N}_3^{-}$
2. $N_2^{-}$
3. $N_3^{-}$
4. $N^{3-}$

Q. Which one of the following is not a conjugate acid-base pair?

1. $HN{O}_2,N{O}_2^{-}$
2. $C{H}_{3}N{H}_3^{+},C{H}_{3}N{H}_2$
3. $H_3{O}^{+},O{H}^{-}$
4. $C_6{H}_{5}COOH,C_6{H}_{5}CO{O}^{-}$

Q. $0.01M$ Solution of $H_{2}A$ has $pH=4$ . If $K_{a_1}$ for the acid is $4.45\times {10}^{-7}$ , the concentration of $H{A}^{-}$ ion in the solution would be :

1. $1.0\times {10}^{-2}M$
2. $4.45\times {10}^{-5}M$
3. $8.0\times {10}^{-5}M$
4. Unpredictable

Q. In the equilibrium $C{H}_{3}COOH+HF\rightleftharpoons C{H}_{3}COO{H}_2^{+}+F^{-}$ which one of the following statement is/are correct?

1. $F^{-}$ is the conjugate base of $HF$
2. $C{H}_{3}COO{H}_2^{+}$ is the conjugate base of $C{H}_{3}COOH$
3. $F^{-}$ is the conjugate acid of $C{H}_{3}COOH$
4. $C{H}_{3}COOH$ is the conjugate acid of $C{H}_{3}COO{H}_2^{+}$

Q. Consider various species generated when $H_{3}P{O}_4$ is dissolved in water. According to the Bronsted Lowry’s Concept among these, the conjugate acid of $HP{O}_4^{2-}$ is :

1. $HP{O}_4^{2-}$
2. $H_{2}P{O}_4^{-}$
3. $P{O}_4^{3-}$
4. $H_3{O}^{+}$

Q. Conjugate base of $HC{O}_3^{-}$ is:

1. $H_{2}C{O}_3$
2. $C{O}_2$
3. $H_{2}O$
4. $C{O}_3^{2-}$

Q.

What will be the conjugate bases for the Brönsted acids: HF, $H_{2}S{O}_4$ and $HC{O}_3$?

Q. Which of the following acts as the strongest conjugate base?

1. $C{H}_{3}CO{O}^{-}$
2. $C{l}^{-}$
3. $N{O}_2^{-}$
4. $S{O}_4^{2-}$

Q. Which of the following species act as an amphiprotic species in the following reactions?
$HCl\left(aq\right)+H_{2}O\left(aq\right)\rightleftharpoons H_3{O}^{+}\left(aq\right)+C{l}^{-}\left(aq\right)$

$N{H}_3\left(aq\right)+H_{2}O\left(aq\right)\rightleftharpoons N{H}_4^{+}\left(aq\right)+O{H}^{-}\left(aq\right)$

1. $N{H}_3$
2. $H_{2}O$
3. $O{H}^{-}$
4. $C{l}^{-}$

Q.

Write the conjugate acids for the following Brönsted bases: $N{H}_2^{-},N{H}_3$ and $HCO{O}^{–}$.

Q. For 0.50 M aqueous solution of sodium cyanide, $\left({\text{pK}}_{\text{b}}{\text{of CN}}^{-}\text{is}4.70\right)$, calculate
(i) Hydrolysis constant
(ii) Degree of hydrolysis
iii) pH
log( 3.15 )=0.498
$\text{Antilog (-9.3)}=5.01\times {10}^{-10}$

1. $2\times {10}^5,6.3\times {10}^{-3},11.5$
2. $2\times {10}^3,6.3\times {10}^{-3},11.5$
3. $4\times {10}^3,6.3\times {10}^{-3},9.5$
4. $2\times {10}^3,4.2\times {10}^{-3},11.5$

Q. Conjugate base for Bronsted acids $H_{2}O$ and $HF$ are

1. $O{H}^{-}$ and $F^{-}$, respectively
2. $O{H}^{-}$ and $H_2{F}^{+}$, respectively
3. $H_3{O}^{+}$ and $F^{-}$, respectively
4. $H_3{O}^{+}$ and $H_2{F}^{+}$, respectively

Q. Consider the equilibrium reaction:
$N{H}_3+H_{2}O\rightleftharpoons N{H}_4^{+}+O{H}^{-}$
Which of the following species can act as a Bronsted-Lowry acid?

1. Both (b) and (c)
2. $N{H}_3$
3. $N{H}_4^{+}$
4. $H_{2}O$

Q. The conjugate acid of $N{H}_2^{-}$ is

1. $N_2{H}_4$
2. $N{H}_{2}OH$
3. $N{H}_3$
4. $N{H}_4^{+}$

Q. Which one of the following is not a conjugate acid-base pair?

1. $HN{O}_2,N{O}_2^{-}$
2. $C{H}_{3}N{H}_3^{+},C{H}_{3}N{H}_2$
3. $H_3{O}^{+},O{H}^{-}$
4. $C_6{H}_{5}COOH,C_6{H}_{5}CO{O}^{-}$

Q. With restpect to $N{H}_3$, Ammonium ion is

1. Neither an acid nor a base
2. Both acid and base
3. A conjugate acid
4. A conjugate base