Question

Calculate the number of moles of helium present in $52\mathrm{g}$ of helium.

Answer 1

Step 1: Analyse the formula to calculate the number of moles.

• The number of moles can be calculated by using the formula:

$\mathrm{Number}\mathrm{of}\mathrm{moles}=\frac{\mathrm{Given}\mathrm{mass}}{\mathrm{Molar}\mathrm{mass}}$

• According to the question, the given mass is $52\mathrm{g}$ and the molecular mass can be calculated.

Step 2: Calculate the molecular mass of Helium.

• To find the molecular mass, we will add the atomic masses of all of the atoms in the molecule.
• In this case, there is only one atom of helium ($\mathrm{He}$) in a molecule of helium gas ($\mathrm{He}$).
• So, the molecular mass of helium gas $=4\mathrm{g}{\mathrm{mol}}^{-1}$

Step 3: Calculate the number of moles.

• The given mass is $52\mathrm{g}$ and the molar mass is $4\mathrm{g}{\mathrm{mol}}^{-1}$
• So, the number of moles of $\mathrm{He}$ are $\frac{52\mathrm{g}}{4\mathrm{g}{\mathrm{mol}}^{-1}}=13\mathrm{moles}$

Hence, the number of moles of helium present in $52\mathrm{g}$ of helium is $13\mathrm{moles}$.