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)

$1.344 \times 10^{21}$ molecules

Answer 2

$\because 22400\, mL$ 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