Question

How many atoms are present in $0.23$ mol of $H_{2}O$?

Answer 1

$1$ mole of $H_{2}O$ molecules $=6.022\times {10}^{23}{H}_{2}O$ molecules

Number of $H_{2}O$ molecules in $0.23$ mol $H_{2}O$ is:

$0.23$ mol $H_{2}O\times \frac{6.022\times {10}^{23}{H}_{2}Omolecules}{1mol{H}_{2}O}=1.38506\times {10}^{23}$ $H_{2}O$ molecules

In a single $H_{2}O$ molecules, there are $3$ atoms $(2-H\&1-O)$

Number of atoms in $1.38506\times {10}^{23}{H}_{2}O$ molecules is:

$1.38506\times {10}^{23}{H}_{2}O\times \frac{3atoms}{1H_{2}Omolecules}=4.15518\times {10}^{23}$ atoms $\approx 4.2\times {10}^{23}$ atoms.