Question

$1 \,mL$ of $0.01 \,N \,HCl$ is added to $999\, mL$ solution of $0.1 \,N \,Na_2SO_4$. The $pH$ of the resulting solution will

• A. 2
• B. 7
• C. 5
• D. 1

Answer 1

Answer: (C)

$As Na _{2} SO _{4}$ solution is neutral, it simply dilutes the $HCl$ solution from $1 \,mL$ to $1000\, mL$.

Now $\left[ H ^{+}\right] =\frac{0.01}{1000}=10^{-5}\, M $

$ \therefore \, pH =-\log \left[ H ^{+}\right] $

$=-\log\, 10^{-5} $

$=[-5 \,\log \,10]$

$pH =5 $