Question

Find the $pH$ value of the mixture containing $50ccMHCl$ and $30ccMNaOH$ solution, assuming both to be completely ionised.

• A. 0.7051
• B. 0.6021
• C. 10.051
• D. 8.052

Answer 1

Answer: (B)

Total volume after mixing $=50+30=80cc$
Moles of $HCl$ after mixing $=\frac{50}{80}M$
Moles of $NaOH$ after mixing $=\frac{30}{80}M$
Remaining number of moles of $HCl$ after mixing
$=\frac{50}{80}-\frac{30}{80}=0.25M$
$\left[H^{+}\right]=0.25=2.5\times 10^{-1}$
$pH=-\log \left[2.5\times 10^{-1}\right]=1-0.3979=0.6021$