Question

Density of water at room temperature is $1.0gc{m}^{-3}$. How many molecules are there in one drop of water if its volume is $0.1c{m}^3$ ?

Answer 1

$334\times {10}^{21}$ molecules
Mass of one drop $=Vol.\times d=0.1\times 1=0.1g$
No. of moles $=\frac{0.1}{18}$ No. of molecules $=6.02\times {10}^{23}\times \frac{0.1}{18}$