Question

If $1 \,mL$ of water contains $20$ drops then number of molecules in a drop of water is

• A. $ 6.023\times 10^{23} $ molecules
• B. $ 1.376\times 10^{26} $ molecules
• C. $1.344 \times 10^{21}$ molecules
• D. $ 4.346\times 10^{20} $ molecules

Answer 1

Answer: (C)

$\because 22400\, mL$ water contains, water molecules
$=6.023 \times 10^{23}$
$\therefore $ In $1 mL$, the number of water molecules
$=\frac{6.023 \times 10^{23}}{22400}$
Since, $1 \,mL$ contains $20$ drops,
therefore, number of water molecules in $1$ drop
$=\frac{6.023 \times 10^{23}}{22400 \times 20}$
$=1.344 \times 10^{18} $ molecules