Equilibrium Question 467
Question: What will be the $ pH $ of a solution formed by mixing $ 40ml $ of $ 0.10MHCl $ with $ 10ml $ of $ 0.45MNaOH $ [Manipal MEE 1995]
Options:
A) 12
B) 10
C) 8
D) 6
Show Answer
Answer:
Correct Answer: A
Solution:
M.eq. of 0.10 $ MHCl=\frac{0.10}{1000}\times 40=0.004M $ M.eq. of 0.45 $ MNaOH=\frac{0.45\times 10}{1000}=0.0045M $ Now left $ [O{H^{-}}]=0.0045-0.004 $
$ =5\times {10^{-4}} $ M Total volume = 50 ml. $ [O{H^{-}}]=\frac{5\times {10^{-4}}}{50}\times 1000 $ ; $ [O{H^{-}}]=1\times {10^{-2}} $ pOH = 2 ; pH = 14 - pOH = 12.
