Solveeit Logo
Login

Question

Chemistry Question on Solutions

The pH of M/100 NaOH solution is :

A

2

B

10

C

6

D

12

Answer

12

Explanation

Solution

NaOH completely ionises as           NaOH→ Na++OH− \, \, \, \, \, \, \, \, \, \, NaOH \rightarrow \, Na^+ +OH^- ∴    [OH−]=[NaOH]=M100=10−2M\therefore \, \, \, \, [OH^-]=[NaOH]=\frac{M}{100}=10^{-2}M Now,as       [H3O+][OH−]=10−14 \, \, \, \, \, \, [H_3O^+][OH^-]=10^{-14} or              [H3O+]=10−14[OH−]=10−1410−2=10−12or \, \, \, \, \, \, \, \, \, \, \, \, \, \, [H_3O^+] =\frac{10^{-14}}{[OH^-]}=\frac{10^{-14}}{10^{-2}}=10^{-12} ∴               pH=−log[H3O+]\therefore \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, pH=-log[H_3O^+]                    =−log 10−12 \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, =-log \, 10^{-12}                    pH=12\, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, pH=12