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.



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