Question

Calculate the number of atoms in each of the following:

16g of He

Answer 1

Helium:

1. The symbol used for Helium gas is $\mathrm{He}$.
2. Helium is a noble gas.
3. It does not participate in bond formation

Weight of Helium ($\mathrm{He}$) given = 16g

The molar mass of $\mathrm{He}$ = 4g

As we know,

$$\begin{gathered} \frac{\mathrm{weight}}{\mathrm{molar}\mathrm{mass}}=\frac{No.ofatoms}{6.02\times {10}^{23}} \\ \frac{16}{4}=\frac{No.ofatoms}{6.02\times {10}^{23}} \\ No.ofatoms=16\times (6.02\times {10}^{23})/4=24.08\times {10}^{23} \end{gathered}$$

Hence, 16g of He will have $\mathit{24}\mathit{.}\mathit{08}\mathit{}\mathit{\times }\mathit{}{\mathit{10}}^{\mathit{23}}$ atoms