Question

A solution of $NaOH$ (Molar mass $40g{mol}^{-1})$ was prepared by dissolving $1.6g$ of $NaOH$ in $500c{m}^3$ of water. Calculate molarity of $NaOH$ solution.

Answer 1

$1$ mol of $NaOH$ has a mass of $40g$. So

Moles of $NaOH=1.6g$ of $NaOH\times \frac{1molNaOH}{40gNaOH}=0.04$ mol $NaOH$

Litres of solution $=500ml$ solution $\times \frac{1LSolution}{1000mlSolution}=0.5$ $L$ Solution

Molarity $=\frac{molesofSolute}{litresofsolution}$

$=\frac{0.04}{0.5}$ mol/L

$=0.08$ mol/L