What is the number of water molecules contained in a drop of water weighing `0.06 g` ?

Explanation

We know that 1 mole of water contains `6.022 xx 10^(23)` water molecules. So, in order to calculate the number of molecules in `0.06` gram of water, we should first calculate the mass of 1 mole of water in grams.
Now, Molecular mass of water, `H_(2)O = 2 + 6`
`= 18 u`
So, Gram molecular mass of water `= 18` grams
(or 1 mole of water)
Thus, 1 mole of water has a mass of 18 grams and it contains `6.022 xx 10^(23)` molecules of water.
Now, `18g` water contains `= 6.022 xx 10^(23)` molecules
So, `0.06 g` water contains `= (6.022 xx 10^(23))/(18) xx 0.06`
`= 2.007 xx 10^(21)` molecules
Thus, a drop of water weighing `0.06` gas contains `2.007 xx 10^(21)` molecules of of water in it.