Question

wht is the no of molecules present in (i) 15 l of h2 gas at stp
(ii) 0.5 g of h2 gas

Answer 1

$$\begin{gathered} \text{Dear Student,} \\ 1.22.4\mathrm{L}\mathrm{of}{\mathrm{H}}_2=1\mathrm{mole} \\ 15\mathrm{L}=\frac{1}{22.4}\times 15=0.6696\mathrm{mole} \\ 2)\mathrm{number}\mathrm{of}\mathrm{moles}=\frac{\mathrm{Given}\mathrm{Mass}}{\mathrm{molar}\mathrm{mass}}=\frac{0.5}{2}=0.25\mathrm{mole} \\ \mathrm{Number}\mathrm{of}{\text{molecules in 1 mole = 6.023 ×10}}^{23}\text{molecules} \\ \mathrm{Number}\mathrm{of}{\text{molecules in 0.25 mole =0.25 ×6.023 ×10}}^{23}\text{molecules = 1.505}\times {10}^{23}\mathrm{molecules} \\ \mathrm{Regards} \end{gathered}$$