Henderson Hassleback Equation

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. 4.34
3. 4.76
4. 2.52

Q.

The pH of a mixture of $0.01M$ $\mathrm{HCl}$ and $0.1M$ ${\mathrm{CH}}_3\mathrm{COOH}$ is approximately

1. $1$

2. $2$

3. $4$

4. $7$

Q. The $p{K}_a$ of a weak acid $\left(HA\right)$ is $4.5$. The $pOH$ of an aqueous buffered solution of $HA$ in which $50\%$ of the acid is ionized is

1. 4.5
2. 2.5
3. 9.5
4. 7

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.

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. If $50\text{mL}$ of $0.2MKOH$ is added to $40\text{mL}$ of $0.5MHCOOH$. The pH of the resulting solution is $(K=1.8\times {10}^{-4})$ :

1. 7.5
2. 3.4
3. 3.75
4. 5.6

Q. The pH of an acid buffer can be raised by 2 units by:

1. Increasing the concentration of both weak acid and salt by two moles
2. Increasing the concentration of both the acid and salt by 10 times
3. Diluting the solution by 10 times
4. Increasing the concentration of the salt by 10 times and decreasing concentration of the acid by 10 times

Q. Choose the correct statement regarding Methyl Orange indicator:

1. Colour transition range for Methyl Orange is nearly $(6-8.6)$
2. Colour transition range for Methyl Orange is nearly $(3.2-4.4)$
3. Colour transition range for Methyl Orange is nearly $(8.3-10)$
4. Colour transition range for Methyl Orange is nearly $(6.2-7.4)$

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.

pH of 0.5 M $Ba(CN{)}_2$ solution $(p{K}_{b}ofC{N}^{-}=9.30)$ is :

1. 8.35

2. 3.35

3. 9.35

4. 9.50

Q. $25mL$ of $0.1N{H}_{3}P{O}_4$ is titrated against $0.1NNaOH$. The $pH$ of the solution after addition of $62.5mL$ of the base is :
(Given : $K_{a1}=1\times {10}^{-3},K_{a2}=1\times {10}^{-8}and{K}_{a3}=1\times {10}^{-13}$)

Q.

pH of 0.5 M $Ba(CN{)}_2$ solution $(p{K}_{b}ofC{N}^{-}=9.30)$ is :

1. 8.35

2. 3.35

3. 9.35

4. 9.50

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. Two buffers, $\left(X\right)$ and $\left(Y\right)$ of $pH$ 4.0 and 6.0 respectively are prepared from acid HA and the salt $NaA$. Both the buffers are $0.50M$ of HA. What would be the pH of the solution obtained by mixing equal volumes of the buffers ? $K_{HA}=1.0\times {10}^{-5}$

1. 8.4
2. 4.3
3. 5.7
4. 7.5

Q. The pKa of a weak acid (HA) is 4.5. The pOH of an aqueous buffered solution of HA in which 50% of the acid is ionized is

1. 4.5
2. 2.5
3. 9.5
4. 7

Q.

What is the threshold below which, if the pH of rain water drops, it is called ‘acid rain’?

1. 5.4

2. 5.6

3. 6.5

4. 6.6

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. $\frac{1}{1}$

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

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

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

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. The $p{K}_b$ of cyanide ion is 4.7 The pH of a solution prepared by mixing 2.5 moles of KCN and 2.5 moles of HCN in water and making total volume upto 500 ml is :

1. 9.3
2. 7.3
3. 10.3
4. 8.3

Q.

They yield of acid amide in the reaction, $RCOCl+N{H}_3\to RCON{H}_2$ , is maximum when

1. Acid chloride and ammonia are treated in equimolar ratio

2. Acid chloride and ammonia are treated in 1 : 2 molar ratio

3. Acid chloride and ammonia are treated in 2 : 1 molar ratio

4. All the three gives nearly similar result

Q. How many $O{H}^{-}$ are present in 1 ml of a solution, whose $pH$= 13

1. $6.02\times {10}^{19}$
2. $6.02\times {10}^{24}$
3. $6.02\times {10}^{-19}$
4. $6.02\times {10}^{-13}$

Q. The pH of an acid buffer can be raised by 2 units by:

1. Increasing the concentration of both weak acid and salt by two moles
2. Increasing the concentration of both the acid and salt by 10 times
3. Diluting the solution by 10 times
4. Increasing the concentration of the salt by 10 times and decreasing concentration of the acid by 10 times

Q. $HCl$ gas is passed through an aqueous solution of 0.1 M 1-aminopropane $\left(PrN{H}_2\right)$ till the pH reaches 9.71. Calculate the ratio of $\left[PrN{H}_2\right]/\left[PrN{H}_3^{+}\right]$ in this solution. $\left[K_a\right(PrN{H}_3^{+})=1.96\times {10}^{-11}]$
$log\left(1.96\right)=0.292,log\left(0.1\right)=-1$

1. 10:1
2. 8:1
3. 4:1
4. 1:10

Q. According to Henderson-Hasselbalch equation, when the pH of a solution becomes equal to its pKa, the solution becomes a buffer. This condition is achieved when ?

1. The concentration of proton donor equals the concentration of proton acceptor
2. Concentration of proton donor become zero
3. Concentration of proton acceptor become zero
4. The concentration of proton donor become log 1/10th of concentration of proton acceptor

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

1. 
2. 
3. 
4. 

Q. $K_a$ for HCN is $5\times {10}^{-10}$ at $25{}^{\circ }C$. For maintaining a constant pH of 9, the volume of $5MKCN$ solution required to be added to $10mL$ of $2MHCN$ solution is $(\log 2=0.3andlog5=0.69)$

1. 4 mL
2. 8 mL
3. 2 mL
4. 10 mL

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.

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. At ${25}^{\circ }C,$ consider $1L$ of two solutions as following:
Solution A : Contains $1molC{H}_{3}COONa+0.5molHCl$
Solution B : Contains $1molC{H}_{3}COONa+0.5molC{H}_{3}COOH$
If $K_a\left(C{H}_{3}COOH\right)={10}^{-5}$ then ratio of [$H^{+}$ (aq.)] of solution A to that of solution B is,
(Given: $log1=0andlog2=0.3,log(5\times {10}^{-6}=-5.3$)

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

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. $\frac{1}{1}$