Thank you for reporting, we will resolve it shortly
Q.
Density of water at room temperature is $1 \,g/ml$. How many molecules are there in a drop of water, if its volume is $0.05 \,ml$?
Some Basic Concepts of Chemistry
Solution:
Density of water at room temperature $= 1 \,g/mol$
$\therefore 1\,ml$ contain $\frac{1}{18}$ moles of $H_2O$
$0.05\,ml$ will contain $0.05 \times \,\frac{1}{18}$ moles
$\therefore 1\,$ mole $ = 6.022 \times 10^{23} $ moles
Total number of molecules in a drop of water
$ = 6.023 \times 10^{23} \times 0.05 \times \frac{1}{18}$
$ = 1.67\times 10^{21}$