Question

What are the number of moles and the number of H atoms present in $9.033\times {10}^{23}$ molecules of water?

• A. $18.066\times {10}^{23}$ atoms, 3 moles
• B. $5.419\times {10}^{24}$ atoms, 9 moles
• C. $24.088\times {10}^{23}$ atoms, 4 moles
• D. $2.8066\times {10}^{24}$ atoms, 3 moles

Answer 1

The correct option is A $18.066\times {10}^{23}$ atoms, 3 moles

The chemical formula of water is $H_{2}O$.
One molecule of water contains two hydrogen atoms.
$\Rightarrow$ $9.033\times {10}^{23}$ molecules of water contain: $2\times 9.033\times {10}^{23}=18.066\times {10}^{23}$ atoms of hydrogen.

Number of moles of hydrogen atoms = $\frac{\mathrm{Number}\mathrm{of}\mathrm{atoms}}{\mathrm{Avogadro}\mathrm{no}.}$=$\frac{18.066\times {10}^{23}}{6.022\times {10}^{23}}$ = 3 moles.

One mole of a substance contains Avogadro's number of particles.
Hence, 3 moles of hydrogen atoms contain = $3\times 6.022\times {10}^{23}$ atoms = $18.066\times {10}^{23}$ atoms.