Acidic Buffer Action

Q. pH of 0.1 M solution of a weak acid (HA) is 4.50. It is neutralised with NaOH solution to decrease the acid content to half of its initial value. Calculate the pH of the resulting solution.

1. 8.00
2. 10.00
3. 4.50
4. 7.00

Q.

An acidic buffer solution can be prepared by mixing the solutions of

1. Sulphuric acid and sodium hydroxide

2. Sodium chloride and sodium hydroxide

3. Ammonium acetate and acetic acid

4. Ammonium chloride and ammonium hydroxide

Q.

An acid type indicator, Hln differs in colour from its conjugate base ($I{n}^{-}$). The human eye is sensitive to colour differences only when the ratio $\frac{\left[I{n}^{-}\right]}{\left[Hln\right]}$ is greater than 10 or smaller than 0.1. What would be the minimum change in pH of the solution to observe a complete colour change ($K_a$ = $1.0\times {10}^{-5}$) ?

1. 2

2. 3.25

3. 6

4. 4

Q. $100\text{mL}$ of a buffer solution contains $0.1\text{M}$ each of weak acid $HA$ and salt $NaA$. How many grams of $NaOH$ should be added to the buffer so that its pH becomes 6? $(K_a\text{of HA}={10}^{-5})$

1. $\text{0.328 g}$
2. $\text{0.458 g}$
3. $\text{4.19 g}$
4. $\text{3.28 g}$

Q. An unknown volume and unknown concentration of a weak acid $HX$ is titrated with $NaOH$ of unknown concentration. After addition of $10.0{\text{cm}}^3$ of the $NaOH$ solution, the $pH$ of the solution is 5.7. After the addition of $20.0{\text{cm}}^3$ of the $NaOH$ solution, the $pH$ is $6.3$. Calculate the $p{K}_a$ of the weak acid, HX. (Given: log2 = 0.3, log = 0.5)

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. 8.62

3. 12.8

4. 4.74

Q. $1\text{L}$ of a buffer solution contains one mole each of $C{H}_{3}COOH$ & ${\left(C{H}_{3}COO\right)}_2\text{Ba}$. Which of the following options are correct? $(p{K}_a\text{of}C{H}_{3}COOH=4.7,\text{log}2=0.3)$

1. pH = 4.7
2. pH = 5
3. pOH = 9
4. pOH = 9.3

Q. $0.1\text{M}C{H}_{3}COOH$ is titrated with $0.1MNaOH$ solution. What would be the difference in pH between $\frac{1}{4^{th}}\text{and}\frac{3}{4^{th}}$ stages of neutralization of the acid?

1. $2\text{log}\left(\frac{1}{4}\right)$
2. $2\text{log 3}$
3. $0.47$
4. $\text{log 2}$

Q. $2\text{g}$ of acetate ions in the form of sodium acetate are added to $500\text{mL}$ of a $0.10\text{M}$acetic acid solution of $p{K}_a\left(C{H}_{3}COOH\right)=4.74$. What is the $pH$ of the final solution?

1. $5.70$
2. $4.56$
3. $5.01$
4. $4.74$

Q. $pH$ of the solution containing equimolar amount of $C{H}_{3}COOH$
$(p{K}_a=4.74)\text{and}C{H}_{3}CO{O}^{-}$ at ${50}^{\circ }C$ is:

1. Less than 4.74
2. More than 4.74
3. None of these
4. Equal to 4.74