Question

Number of molecules in one litre of water is close to:

• A. $55.5 \times 6.023 \times 10^{23}$
• B. $18 \times 6.023 \times 10^{23}$
• C. $18 \div 22.4 \times 10^{23}$
• D. $1.8 \times 10^{23}$

Answer 1

Answer: (A)

$1 \,L\,H _{2} O =1000\, cc =1000\, g$
$\therefore 18\, g$ of $H_{2} O =6.023 \times 10^{23}$ molecules
$\therefore 1000\, g$ of $H_{2} O =\frac{6.023 \times 10^{23} \times 1000}{18}$
$=6.023 \times 10^{23} \times 55.5$ molecules