Question

The $pH$ value of decinormal solution of $NH_4OH$ which is $20\%$ ionised is

• A. 12.95
• B. 12.3
• C. 14.7
• D. 13.3

Answer 1

Answer: (B)

12.3

Answer 2

Concentration of $NH_4OH$ solution $= 0.1\, N$ Concentration of $OH$ - ions in solution, $\left[OH^{-}\right] = 20\%$ of $0.1\, N = \frac{20}{100}\times 0.1$ $= 0.02\, N$ $\Rightarrow pOH = - \left[logOH^{-}\right] = - log \left(0.02\right)$ $= 2 - 0.301$ $\Rightarrow pH = 14 - pOH = 12.30$