Question

Calculate the weight of $NaOH$ present in $500ml$ of $0.2M$ $NaOH$ solution.

Answer 1

given : molarity of the solution = $0.2M$

i.e, $0.2$ moles of $NaOH$ are present per litre of the solution.

so no. of moles of $NaOH$ in $500ml$ of the solution is :

$0.2\times \frac{500mL}{1L}=0.2\times \frac{1}{2}=0.1$ moles

molar mass of $NaOH$ = molar mass of $(Na+O+H)=23+16+1=40g$

so mass of $0.1$ mole $NaOH=40\times 0.1=4g$