Number of molecules present in 10 g of  ${\text{H}}_2$

$2{\text{\hspace{0.17em}g\hspace{0.17em}of\hspace{0.17em}H}}_2\to 6.02\times {10}^{23}{\text{H}}_{\text{2}}\text{\hspace{0.17em}molecules}$

$10{\text{\hspace{0.17em}g\hspace{0.17em}of\hspace{0.17em}H}}_2\to \text{'}\text{X\hspace{0.17em}}\text{'}{\text{\hspace{0.17em}\hspace{0.17em}H}}_{\text{2}}\text{\hspace{0.17em}molecules}$

$\text{X}=10\text{\hspace{0.17em}g}\times \frac{6.02\times {10}^{23}\text{\hspace{0.17em}molecules\hspace{0.17em}of H2\hspace{0.17em}}}{2\text{\hspace{0.17em}g}}$

$\therefore x=3.01\times {10}^{24}{\text{\hspace{0.17em}\hspace{0.17em}H}}_2\text{\hspace{0.17em}molecules}$