Question

The number of atoms of hydrogen present in 12.0 g of water is :

• A. $1.1\times {10}^{23}$
• B. $2.0\times {10}^{23}$
• C. $4.0\times {10}^{23}$
• D. $8.0\times {10}^{23}$
• E. $4.8\times {10}^{24}$

Answer 1

Answer: (D)

$8.0\times {10}^{23}$

The molar mass of water is 18 g/mol.
12.0 g of water corresponds to $\frac{12}{18}=0.67$ moles.
1 mole of water contains $6.023\times {10}^{23}$ molecules of water or
$2\times 6.023\times {10}^{23}=12.046\times {10}^{23}$ atoms of hydrogen.
Hence, 12 g of water contains $0.67\times 12.046\times {10}^{23}=6.023\times {10}^{23}=8.0\times {10}^{23}$ hydrogen atoms.