Buffer Solutions

Q. If 0.01 mole of NaOH is added to 1 litre solution of a basic buffer having $pH=8.7$ initially, the $pH$ changes to 9. Calculate the buffer capacity of the buffer.

1. 0.33
2. 0.033
3. 0.087
4. 0.02

Q. In some solutions, the concentration of $H_3{O}^{+}$ remains constant even when small amounts of strong acid or strong base are added to them. These solutions are known as:

1. Colloidal solutions
2. Buffer solutions
3. True solutions
4. Ideal solutions

Q.
Which of the following will function as buffer?

1. $Na{H}_{2}P{O}_4+N{a}_{2}HP{O}_4$
2. $C_6{H}_{5}N{H}_2+C_6{H}_{5}N{H}_3^{+}C{l}^{-}$
3. $N{H}_{4}Cl+N{H}_{4}OH$
4. All of the above.

Q. Which one of the following set of solute will form a buffer solution when dissolved in water to make 1 Litre of solution ?

1. 4 mole of $N{H}_3$ with 2 mole of $HCl$
2. 2 mole of $NaCl$ with 2 mole of $HCl$
3. 4 mole of $C{H}_{3}COOH$ with 4 mole of $NaCl$
4. 0.002 mole of $HCl$

Q. $p{K}_a$ of weak acid is 3.0 . Effective range of a buffer of $HA$ and $A^{-}$ is :

1. 3 to 4
2. 4 to 6
3. 2 to 3
4. 2 to 4

Q. Which of the following equimolar mixture can act as a salt buffer ?

1. $C{H}_{3}COOH+C{H}_{3}COONa$
2. $N{H}_{4}OH+N{H}_{4}Cl$
3. 
   $N{H}_{4}OH+C{H}_{3}COOH$
4. $HCl+NaOH$

Q. Consider an aqueous solution containing a weak acid $C{H}_{3}COOH$ and a strong base $NaOH$ at ${25}^{\circ }C$
This can act as an acidic buffer when :

1. Molar concentration of weak acid is more than the concentration of strong base i.e $\left[C{H}_{3}COOH\right]>\left[NaOH\right]$
2. Molar concentration of weak acid is less than the concentration of strong base i.e $\left[C{H}_{3}COOH\right]<\left[NaOH\right]$
3. Molar concentration of weak acid is equal to the concentration of strong base i.e $\left[C{H}_{3}COOH\right]=\left[NaOH\right]$
4. An acidic buffer is always formed by $C{H}_{3}COOH$ and $NaOH$

Q. $20mL$ of $0.1M{H}_{2}S{O}_4$ solution is added to $30mL$ of $0.2MN{H}_{4}OH$ solution. The $pH$ of the resultant mixture is $[p{K}_{b}ofN{H}_{4}OH=4.7,\log 2=0.3010]$

1. 5.2
2. 9
3. 9.4
4. 5

Q. Which of the following can be used as a buffer solution?

1. A solution containing $NaCl$ and $NaOH$.
2. A solution containing $NaCl$ and $N{H}_{4}OH$.
3. A solution containing sodium acetate.
4. A solution containing ammonium acetate.

Q. Aqueous solution of $HN{O}_3,KOH,C{H}_{3}COOH$ and $C{H}_{3}COONa$ of identical concentration are provided. The pair(s) of solution which forms buffer upon mixing is (are)

1. $KOH\text{and}C{H}_{3}COONa$
2. $HN{O}_3\text{and}C{H}_{3}COOH$
3. $HN{O}_3\text{and}C{H}_{3}COONa$
4. $C{H}_{3}COOH\text{and}C{H}_{3}COONa$

Q. Buffer capacity is maximum when the ratio , $\left(\frac{\text{[Anion of salt]}}{\text{[Acid]}}\right)$ is :

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

Q. A buffer solution is prepared by mixing 10 ml of 1.0 M acetic acid and 20 ml of 0.5 M sodium acetate and then diluted to 100 ml with distilled water. If the $p{K}_a$ of $C{H}_{3}COOH$ is 4.76, what is the pH of the buffer solution prepared?

1. 5.21
2. 4.76
3. 4.34
4. 5.21

Q. Which of the following will form a buffer solution?
(a) $C{H}_{3}COONa+C{H}_{3}COOH$
(b) $NaCl+NaOH$
(c) $N{H}_{4}Cl+N{H}_{4}OH$
(d) $N{a}_{2}S{O}_4+H_{2}S{O}_4$

1. A, B
2. B, C
3. A, C
4. A, D

Q. Which one of the following is natural buffer ?

1. Blood
2. River water
3. (a) and (b) above.
4. None of the above

Q. Which one is incorrect regarding the representation of buffer index ?

1. $\frac{\left[\text{Conjugate base}\right]}{\left[\text{Weak Acid}\right]}<0.1$
2. $\frac{\left[\text{Conjugate acid}\right]}{\left[\text{Weak Base}\right]}<10$
3. $\frac{\left[\text{Conjugate base}\right]}{\left[\text{Weak Acid}\right]}>0.1$
4. None of the above

Q.

On the addition of a small amount of an acid or a base, the pH value of a buffer solution:

1. increases

2. decreases

3. remains unaltered

4. none of these

Q. Which one of the following is natural buffer ?

1. Blood
2. River water
3. (a) and (b) above.
4. None of the above

Q. An example of a basic buffer is:

1. $N{H}_{4}OH+NaCl$
2. $NaCl+HCl$
3. $N{H}_{4}OH+N{H}_{4}Cl$
4. $N{H}_{4}OH+HCl$

Q. What volume of $0.1M$ sodium formate solution should be added to 50 mL of $0.05M$ formic acid to produce a buffer solution of $pH=4.0$?
$(p{K}_a$ of formic acid $=3.80)$
(antilog 1.59 =39.62)

1. 3.96 mL
2. 39.6 mL
3. 45 mL
4. 35.6 mL

Q. What volume of $0.1M$ sodium formate solution should be added to 50 mL of $0.05M$ formic acid to produce a buffer solution of $pH=4.0$?
$(p{K}_a$ of formic acid $=3.80)$
(antilog 1.59 =39.62)

1. 3.96 mL
2. 39.6 mL
3. 45 mL
4. 35.6 mL

Q. A buffer solution that has a pH of $4.72$ is prepared by mixing of $1\text{M NaOH}$ and $1M\text{HCN}$. What is the ratio of volumes of the acid to the base? $(p{K}_b{\text{of CN}}^{-}=9.28)$

1. 1 : 1
2. 1 : 2
3. 2 : 1
4. 3 : 1

Q. Which of the following is correct for indentification of the polyacidic bases and polybasic acids respectively?

1. $H_{3}P{O}_4$ and $B(OH{)}_3$
2. $Mg(OH{)}_2$ and $B(OH{)}_3$
3. $Mg(OH{)}_2$ and $H_{2}S{O}_4$
4. $NaOH$ and $H_{3}P{O}_4$

Q. Which of the following mixtures in aqueous solution acts as a buffer?

1. $HN{O}_3+KN{O}_3$
2. $H_{2}S{O}_4+K_{2}S{O}_4$
3. $N{H}_{4}OH+N{H}_{4}Cl$
4. $C{H}_{3}COOH+NaCl$

Q. $p{K}_a$ of weak acid is 3.0 . Effective range of a buffer of $HA$ and $A^{-}$ is :

1. 3 to 4
2. 4 to 6
3. 2 to 3
4. 2 to 4

Q. $0.1$ mole arsenic acid $\left(H_{3}As{O}_4\right)$ is dissolved in a 1L buffer solution of $pH=8$. Which of the following options is/are correct? For arsenic acid: $K{a}_1=2.5\times {10}^{-4},K{a}_2=5\times {10}^{-8},K{a}_3=2\times {10}^{-13}$.
(‘<<’ sign denotes that the higher concentration is 100 times greater than the lower one or more)

1. $\left[H_{3}As{O}_4\right]<<\left[H_{2}As{O}_4^{-}\right]$
2. $\left[H_{2}As{O}_4^{-}\right]<<\left[HAs{O}_4^{2-}\right]$
3. $\left[HAs{O}_4^{2-}\right]<<\left[H_{2}As{O}_4^{-}\right]$
4. $\left[As{O}_4^{3-}\right]<<\left[HAs{O}_4^{2-}\right]$

Q. $p{K}_a$ of weak acid is 3.0 . Effective range of a buffer of $HA$ and $A^{-}$ is :

1. 3 to 4
2. 4 to 6
3. 2 to 3
4. 2 to 4

Q.

Which of the following is not a buffer solution?

1. Ammonium chloride + ammonium hydroxide

2. Sodium acetate + acetic acid

3. NaOH + HCl

4. Sodium formate + formic acid

Q. A solution of weak acid $HA$ was titrated with base $NaOH$. The equivalent point was reached when $40mL$ of $0.1MNaOH$ has been added. Now $20mL$ of $0.1MHCl$ were added to titraded solution, the $pH$ was found to be $5.0$. What will be the $pH$ of the solution obtained by mixing $20mL$ of $0.2MNaOH$ and $20mL$ of $0.2MHA$?