Question

Two aqueous solutions P and Q have pH 5 and 13 respectively. The correct inference is that

• A. Solution P is of $\mathrm{HCl}$and Q is of ${\mathrm{NH}}_4\mathrm{OH}$
• B. Solution P is of ${\mathrm{CH}}_3\mathrm{COOH}$ and Q is of $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$
• C. solution P is of ${\mathrm{HNO}}_3$ and Q is of ${\mathrm{NH}}_4\mathrm{OH}$
• D. Solution P is of ${\mathrm{CH}}_3\mathrm{COOH}$ and Q is of $\mathrm{NaOH}$

Answer 1

The correct option is B

Solution P is of ${\mathrm{CH}}_3\mathrm{COOH}$ and Q is of $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$

The explanation for the correct option:

(B) Solution P is of ${\mathrm{CH}}_3\mathrm{COOH}$ and Q is of $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$

1. Solutions that are acidic in nature have a pH of less than 7 whereas solutions neutral or basic in nature have a pH equal to 7 or more than 7.
2. Solution P has a pH of 5, which is somewhat lower than the neutral pH of 7.
3. As a result, P will be a weak acid, and ethanoic acid is an example of it.
4. Solution Q has a pH of 13, which is somewhat lower than the basic pH of 14.
5. As a result, Q will be a strong base, and calcium hydroxide $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$ is one such strong base.

Explanation for incorrect option(s):

(A) Solution P is of ${\mathrm{CH}}_3\mathrm{COOH}$ and Q is of $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$

Solution P is a weak acid and $\mathrm{HCl}$ is not a weak acid and solution Q is a strong base but ${\mathrm{NH}}_4\mathrm{OH}$ is not a strong base.

(C) Solution P is of ${\mathrm{HNO}}_3$ and Q is of ${\mathrm{NH}}_4\mathrm{OH}$

Solution P is a weak acid as it has a pH of 5 but ${\mathrm{HNO}}_3$ is a strong acid and solution Q is a strong base but ${\mathrm{NH}}_4\mathrm{OH}$ is a weak base.

(D) Solution P is of ${\mathrm{CH}}_3\mathrm{COOH}$ and Q is of $\mathrm{NaOH}$

${\mathrm{CH}}_3\mathrm{COOH}$ is a weak acid and $\mathrm{NaOH}$ is a less strong base because it dissociates only 1 hydroxide ion whereas $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$ dissociates into 2 hydroxide ions.

Hence, the correct answer is an option (B).