Question

Kw of H2O at 373 K is 1 × 10–12. Identify which of the following is incorrect.

• A. pKw of H2O is 12
• B. pH of H2O is 6
• C. H2O is neutral
• D. H2O is acidic

Answer 1

Answer: (D)

H2O is acidic

Answer 2

pKw = – logKw = – log 1 × 10–12 = 12.

Kw = [H+][OH–] = 10–12 .

[H+] = [OH–]

$\Rightarrow$ [H+]2 = 10–12 ; [H+] = 10–6 ; pH = – log[H+]

= – log 10–6 = 6.

H2O is neutral because [H+] = [OH–] at 373 K even when pH = 6.

(4) is not correct at 373 K. Water cannot become acidic.