Question

Calculate the number of molecules in a drop of water weighing $0.05$ gm.

Answer 1

The molecular mass of water = $18g/mol$

The number of moles of water$=n=\frac{weight}{Molecularwt.}=\frac{0.05}{18}=2.78\times {10}^{-3}$

Now, the number of molecules of water$=n\times 6.022\times {10}^{23}$

$=2.78\times {10}^{-3}\times 6.022\times {10}^{23}$

$=1.67\times {10}^{21}$ molecules