Which of the following will decrease the pH of a 50 ml solution of `0.01 M HCI` ?

Options

A. Addition of 50 mL of 0.01 MHCI
B. Addition of 50 mL of 0.002 M HCl
C. Addition of 150 mL of 0.002 M HCl
D. Addition of 5 mL of 1 MHCI

Answer

D

Explanation

For 0.01 M HCl, `pH=-log[10^(-2)]=2`
Using formula, `N_(1)V_(1)+N_(2)V_(2)=NV`
where `V=(V_(1)+V_(2))`
`50xx0.01+5xx1=Nxx55`
`N=(0.5+5)/(55)=0.1`
`pH=-log[10^(-1)]=1` (pH decreased)