Question

Which of the following statements is correct about an aqueous solution of an acid and of a base?

(i) Higher the pH, the stronger the acid

(ii) Higher the pH, weaker the acid

(iii) Lower the pH, stronger the base

(iv) Lower the pH, weaker the base.

• A. (i) and (iii)
• B. (ii) and (iii)
• C. (i) and (iv)
• D. (ii) and (iv)

Answer 1

The correct option is D

(ii) and (iv)

Explanation for the correct options:

(D) (ii) and (iv)

• (ii) In an aqueous solution, the strong acid dissociates and releases more cationic hydrogen$\left({\mathrm{H}}^{+}\right)$ ions so the pH ranges between $0-3$.
• (iv) In an aqueous solution, the strong bases dissociate completely and release hydroxide $\left({\mathrm{OH}}^{-}\right)$ ions, therefore pH ranges between $12-14$.

Explanation for the incorrect options:

(A)(i) and (iii)

• (i) The pH scale ranges from 0-14, where 0 indicates most acidic and 14 indicates most basic, therefore higher the pH, the lower the acid.
• (iii) The pH scale ranges from 0-14, where 0 indicates the most acidic and 14 indicates the most basic, therefore lower the pH, the stronger the acid.

(B)(ii) and (iii)

• (ii) In an aqueous solution, the strong acid dissociates and releases more cationic hydrogen$\left({\mathrm{H}}^{+}\right)$ ions so the pH ranges between $0-3$.
• (iii) The pH scale ranges from 0-14, where 0 indicates the most acidic and 14 indicates the most basic, therefore lower the pH, the stronger the acid.

(C) (i) and (iv)

• (i) The pH scale ranges from 0-14, where 0 indicates most acidic and 14 indicates most basic, therefore higher the pH, the lower the acid.
• (iv) In an aqueous solution, the strong bases dissociate completely and release hydroxide $\left({\mathrm{OH}}^{-}\right)$ ions, therefore pH ranges between $12-14$.

Hence, option (D) is correct, (ii) and (iv) is the correct statement about an aqueous solution of an acid and of a base.