Question

The pH of a solution prepared by mixing 2 M, 100 mL $HCl$ and 1 M, 200 mL NaOH at ${25}^{o}C$ is:

• A. 8
• B. 7
• C. 4
• D. 5

Answer 1

Answer: (B)

7

$NaOH+HCl⟶NaCl+H_{2}O$

As NaOH is strong base can neutralise with strong acid to give neutral salt and water.

Molarity $=\frac{molesof.Solute}{VolumeofsolutioninLitres}$

In HCl

$2M=\frac{molesofHCl}{0.1}$

Moles of HCl=0.2.

In NaOH,

$1M=\frac{molesofNaOH}{0.2}$

Moles of NaOH=0.2

According to the above balanced equation , it neutralised and results as $pH=7$