Question

How many moles of HCl must be removed from 1 liter of aqueous HCl solution to change its pH from 2 to 3?

• A. 1
• B. 0.02
• C. 0.009
• D. 0.01

Answer 1

Answer: (C)

0.009

$HCl$ is the strong acid and dissociates completely.

$HCl\rightleftharpoons H^{+}+C{l}^{-}$

$P^H=-log{H}^{+}$

For $P^H=2=>{10}^{-2}mol/L$

For $P^H=3=>{10}^{-3}mol/L$

$\therefore$ the number of moles of HCl must be removed from 1 Liter$HCl={10}^{-2}-{10}^{-3}=0.009moles.$