Question

Find the volume of $H_{2}O$ that should be added to $300\text{mL}$ of $0.5\text{M}NaOH$ so as to prepare a solution of $0.2\text{M}$.

• A. $750\text{mL}$
• B. $300\text{mL}$
• C. $450\text{mL}$
• D. $150\text{mL}$

Answer 1

The correct option is C $450\text{mL}$

During dilution of a solution, the number of moles of solute is not changing.
$M_1=0.5M$
$V_1=300\text{mL}$
$M_2=0.25M$
We know that $M_1{V}_1=M_2{V}_2\Rightarrow V_2=\frac{M_1{V}_1}{M_2}=\frac{300\times 0.5}{0.2}=750\text{mL}$
So, volume of water to be added $=750-300=450\text{mL}$