The number of molecules present in a drop of water, if its volume is $0.05$ mL and density 1g/mL are:

The correct option is B $1.66\times {10}^{21}$

ANS; A

Mass of water =$0.05\times 1$ = 0.05 gm

In 1 mole of water = 18 gm

In 0.05 gm of water = $\frac{0.05}{18}$

= 0.0027 mole

In 0.05 gm number of molecule = $0.0027\times 6.022\times {10}^{23}$

= $1.66\times {10}^{21}$