Equilibrium Question 454
Question: The $ pH $ value of decinormal solution of $ NH_4OH $ which is 20% ionised, is [CBSE PMT 1998]
Options:
A) 13.30
B) 14.70
C) 12.30
D) 12.95
Show Answer
Answer:
Correct Answer: C
Solution:
For $ NH_4OH $ . $ [O{H^{-}}]=C,.,\alpha $ ; $ C=\frac{1}{10}M $ , $ \alpha =0.2 $
$ [O{H^{-}}]=\frac{1}{10}\times 0.2=2\times {10^{-2}},M $
$ pOH=-\log [O{H^{-}}] $
$ =\log [2\times {10^{-2}}] $ ; $ pOH=1.7 $
$ pH=14-pOH $
$ =14-1.7=12.30 $ .
