Question

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

Answer 1

Step 1:

We know that, Atomic mass of Helium ($\mathrm{He}$) is $4$ a.m.u.

$1\mathrm{atoms}\mathrm{of}\mathrm{He}=4\mathrm{a}.\mathrm{m}.\mathrm{u}$

$1a.m.u.=\frac{1}{4}atomsof$ $\mathrm{He}$

Step 2:

$52a.m.u.=\left(\frac{1}{4}\times 52\right)atomsofHe$

$=13atomsofHe.$

We get that $52a.m.u.$of $\mathrm{He}$ contains $13$ atoms of $\mathrm{He}$.