Henderson Hassleback Equation

Q. The pH of a buffer solution containing 2.0 mol per litre $C{H}_{3}COONa$ and 1.5 mol per litre $C{H}_{3}COOH$ is: ($K_a$ for acetic acid is $1.8\times {10}^{-5})$

1. 4.87
2. 5.8
3. 2.4
4. 9.2

Q.

To 1L solution containing 0.1 mol each of $N{H}_3$ and $N{H}_{4}Cl,0.05$ mol of NaOH is added. The change in pH will be $(p{K}_{b}forN{H}_3=4.74)$

1. -0.48

2. 0.48

3. 0.30

4. -0.30

Q. $p{K}_a$ of $C{H}_{3}COOH$ is 4.74. Thus, the buffer range for $C{H}_{3}COOH$ and $C{H}_{3}COONa$ buffer is

1. 3.74 to 4.74
2. 4.74 to 5.74
3. 3.74 to 5.74
4. 1.0 to -1.0

Q. When $100\text{mL}$ of $0.4MC{H}_{3}COOH$ is mixed with $100\text{mL}$ of $0.2MNaOH$, the approximate value of $\left[H_3{O}^{+}\right]$ in the solution mixture is? $\left[K_a\right(C{H}_{3}COOH)=1.8\times {10}^{-5}]$

1. $1.8\times {10}^{-6}$
2. $1.8\times {10}^{-5}$
3. $9\times {10}^{-6}$
4. $9\times {10}^{-5}$

Q.

Calculate the pH of a solution of 0.10 M acetic acid after 50.0 mL of 0.10 M acetic acid solution is treated with 25.0 mL of 0.10 M NaOH. ($K_a$ of acetic acid = $1.8\times {10}^{-5}$)

1. 5.6

2. 4.74

3. 8.62

4. 12.8

Q. What volume of $0.1MHCOONa$ solution should be added to $50\text{mL}$ of $0.05M$ formic acid to produce a buffer solution of $pH=4.0$, $p{K}_a$ of formic acid $=3.7$ ?

1. $60\text{mL}$
2. $40\text{mL}$
3. $30\text{mL}$
4. $50\text{mL}$

Q.

To what volume one litre of 0.1M acetic acid solution diluted so that the pH of the solution becomes double of the initial ? ( $K_a=1.8\times {10}^{-5}$)

1. $5.5\times {10}^{5}L$

2. $8\times {10}^{4}L$

3. $2.4\times {10}^{3}L$

4. $3.6\times {10}^{8}L$

Q. Draw the Lewis structures for the following molecules and ions :

Q.

Calculate the pH of a solution of 0.10 M acetic acid after 50.0 mL of 0.10 M acetic acid solution is treated with 25.0 mL of 0.10 M NaOH. ($K_a$ of acetic acid = $1.8\times {10}^{-5}$)

1. 5.6

2. 4.74

3. 8.62

4. 12.8

Q.

The base imidazole has $K_b$ of $1.0\times {10}^{-7}$. What volumes of 0.02 M HCl and 0.02 M imidazole should be mixed to make 150 mL of a buffer of pH 7 ?

1. 100 ml and 50 ml

2. 50 mL and 100 mL

3. 75 ml and 75 ml

4. 60 ml and 90 ml

Q. What volume of $0.1MHCOONa$ solution should be added to $50\text{mL}$ of $0.05M$ formic acid to produce a buffer solution of $pH=4.0$, $p{K}_a$ of formic acid $=3.7$ ?

1. $60\text{mL}$
2. $40\text{mL}$
3. $30\text{mL}$
4. $50\text{mL}$

Q. The concentration of $HCN$ and $NaCN$ in a solution is $0.01M$ each. Calculate the concentration of hydroxyl ions if the dissociation constant of $HCN$ is $7.2\times {10}^{-10}$.

1. $14\times {10}^{-7}M$
2. $14\times {10}^{-5}M$
3. $1.4\times {10}^{-5}M$
4. $1.4\times {10}^{-7}M$

Q. Calculate ${\Lambda }_{HN{O}_3}^0$ and ${\Lambda }_{HOAc}^0$ using appropriate molar conductances of the electrolytes listed below at infinite dilution in $H_{2}O$ at ${25}^{\circ }C$.

Electrolyte	${\Lambda }^0\left(Sc{m}^{2}mo{l}^{-1}\right)$
$KCl$	$149.9$
$NaCl$	$126.5$
$HCl$	$426.2$
$KN{O}_3$	$145.0$
$NaOAc$	$91.0$

1. ${\Lambda }_{HN{O}_3}^0=421.3Sc{m}^2{\text{mol}}^{-1}$
   ${\Lambda }_{HOAc}^0=390.7Sc{m}^2{\text{mol}}^{-1}$
2. ${\Lambda }_{HN{O}_3}^0=517.2Sc{m}^2{\text{mol}}^{-1}$
   ${\Lambda }_{HOAc}^0=149.8Sc{m}^2{\text{mol}}^{-1}$
3. ${\Lambda }_{HN{O}_3}^0=390.7Sc{m}^2{\text{mol}}^{-1}$
   ${\Lambda }_{HOAc}^0=517.2Sc{m}^2{\text{mol}}^{-1}$
4. ${\Lambda }_{HN{O}_3}^0=149.8Sc{m}^2{\text{mol}}^{-1}$
   ${\Lambda }_{HOAc}^0=444.7Sc{m}^2{\text{mol}}^{-1}$

Q. Which of the following plots will not be obtained for a conductometric titration of $HCl\text{and}NaOH$?

1. 
2. 
3. 
4. 

Q. To $100mL$ of $0.1M$ $H_{3}P{O}_4$ $200mL$ of $0.1M$ $NaOH$ was added. Calculate the $pH$ of the resulting solution.
($Given{K}_{a1}={10}^{-3},K_{a2}={10}^{-8},K_{a3}={10}^{-13}$)

Q. Calculate the pH of a $0.01MN{H}_{4}OH$ solution containing 1 mol/litre of $N{H}_{4}Cl$ ? $(p{K}_b=4.76)$

1. 6.8
2. 7.24
3. 8.4
4. 7

Q. A weak acid $HA$ after treating with $12\text{mL}$ of $0.1M$ strong base $BOH$ has a $pH$ of 5. At the end point the volume of same base required is $26.6\text{mL}$. Calculate the $K_a$ of an acid.

1. $1.8\times {10}^{-5}$
2. $8.22\times {10}^{-6}$
3. $1.8\times {10}^{-6}$
4. $8.2\times {10}^{-5}$

Q.

The base imidazole has a $K_b$ of $9.8\times {10}^{-8}$ at ${25}^{\circ }$ C.

In what ratio of volumes should 0.02 M HCl and 0.02 M imidazole be mixed to make 100 ml of a buffer at pH 7 ?

1. $\frac{3}{5}$

2. $\frac{2}{3}$

3. $\frac{1}{2}$

4. $\frac{1}{1}$

Q.

To what volume one litre of 0.1M acetic acid solution diluted so that the pH of the solution becomes double of the initial ? ( $K_a=1.8\times {10}^{-5}$)

1. $5.5\times {10}^{5}L$

2. $8\times {10}^{4}L$

3. $2.4\times {10}^{3}L$

4. $3.6\times {10}^{8}L$