# Number of $H^+$ ions in 100ml of 0.001M $H_2SO_4$ is

$\begin{array}{1 1}(a)\;6\times 10^{20}&(b)\;1.2\times 10^{18}\\(c)\;12\times 10^{18}&(d)\;1.2\times 10^{20}\end{array}$

Meq of $H_2SO_4=100\times 0.001=0.1$
1000mM of $H_2SO_4$=2 mole $H^+$
$\therefore$ 0.1mM $H_2SO_4=\large\frac{2\times 0.1\times 6\times 10^{23}}{1000}$
$\Rightarrow 1.2\times 10^{20}$
Hence (d) is the correct answer.