Question

Calculate the number of atoms in 52 u of $\mathrm{He}$.

Answer 1

• One mole contains $6.022\times {10}^{23}$ atoms.

$$\begin{gathered} \mathrm{One}\mathrm{mole}\mathrm{of}\mathrm{He}=4\mathrm{u} \\ \mathrm{Number}\mathrm{of}\mathrm{moles}\mathrm{in}52\mathrm{u}\mathrm{of}\mathrm{He}=52/4 \\ =13\mathrm{moles} \\ \mathrm{Number}\mathrm{of}\mathrm{atoms}\mathrm{in}13\mathrm{moles}=13\times 6.022\times {10}^{23} \\ =7.8286\times {10}^{24} \end{gathered}$$