Question

The pH of solution formed by mixing 40 mL of 0.10 M HCl with 10 mL of 0.45 M of NaOH is

• A. 10
• B. 12
• C. 8
• D. 6

Answer 1

Answer: (B)

Millimoles of $HCl=40\times 0.1=4;$
Millimoles of $NaOH=10\times 0.45=4.5$
Millimoles of $NaOH$ left $=0.5$
$\therefore$ Volume of solution $=50$ mL
$\therefore$ Moles of $NaOH$ per litre
$=\frac{0.5\times 10^{-3}\times 1000}{50}=1\times 10^{-2}M$
$\therefore$ pOH of solution $=-log(1\times 10^{-2})=2$
$\therefore pH=14-2=12$