The pH of a 0.001 M aqueous solution of sodium hydroxide will be

Options

A. 5
B. 7.5
C. 9
D. 11

Answer

D

Explanation

Concentration of NaOH i.e., `[OH^(-)] = 0.001 M = 10^(-3)`
`:. [H^(+)][OH^(-)] = 10^(-14)`
`[H^(+)][10^(-3)] = 10^(-14)`
`[H^(+)] = 10^(-14)/10^(-3)`
`[H^(+)] = 10^(-11) M`
`pH = -"log"[H^(+)] = -"log"[10^(-14)] = -(-11)"log"_(10) = 11`