Question

Assuming the human body to be $80%$ water, the number of molecules of water present in the body of a person, of mass $65\, kg$, are

• A. $1.73 \times 10^{16}$
• B. $17.39 \times 10^{26}$
• C. $173.9 \times 10^{28}$
• D. $1.739 \times 10^{51}$

Answer 1

Answer: (B)

$100$ $kg$ of human body contains $80$ $kg$ of $H_2O$
$65$ $kg$ of human body contains $= \frac{80}{100} \times 65 = 52$ $kg$
$18$ $g$ of $H_{2}O$ contains $= N_{0}$ molecules
$52 \times 10^{3}$ $g$ of $H_{2}O$ contains $= \frac{N_{0}}{18} \times 52 \times 10^{3}$ molecules