Question

The number of helium atoms present in $320\mathrm{amu}$ helium is

Answer 1

Step1. Amu

• A.m.u. is the atomic mass unit that itself represents the mass.

Step2. The formula for the number of atoms

$\text{Number of atoms=}\frac{\mathrm{Total}\mathrm{mass}\mathrm{of}\mathrm{atom}}{\mathrm{Mass}\mathrm{of}\mathrm{one}\mathrm{atom}}$

Step3. Calculation of number of helium atoms

Mass of helium atom is $4\text{amu}$.

$$\begin{gathered} \text{Number of atoms=}\frac{320\text{amu}}{4\text{amu}} \\ \text{=80} \end{gathered}$$

Hence, the number of helium atoms present in $320\mathrm{amu}$ helium is $80$.