The number of molecules in 100 ml of$0.02 \mathrm{N} {\mathrm{H}}_2{\mathrm{SO}}_4$ is

Molarity of acid = Normality /basicity ;

Molarity $=0.02/2=0.01\mathrm{M};1000\mathrm{mL}$

$=0.01\mathrm{mol}$, so $100\mathrm{mL}$

$\begin{array}{l}=0.01\times 100/1000\mathrm{mL}\\ =0.001\mathrm{mol}\text{ or }6.02\times {10}^{23}\times 0.001\\ =6.02\times {10}^{20}.\end{array}$