Calculate the number of molecules in a drop of water weighing 0.05g (H=1, O= 16)

Explanation

We are given that
Molecular mass of `H_(2)O= 18g`
Weight of a water drop = 0.05g
We know that, 18g of water has molecules= `6.023 xx 10^(23)` (Avogadro.s number)
We are to calculate the numbr of molecules in a drop of water weighing 0.05g.
`therefore` 0.05g of water has molecules `= (6.023 xx 10^(23))/(18) xx 0.05 = (6.023 xx 10^(23) xx 5)/(18 xx 100)= 1.67 xx 10^(21)`