Question

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

Answer 1

Number of moles = given mass/molar mass
Given mass = 0.06 g
Molar mass of water = 18g/mol
Numbe of moles = 0.06/18
= 0.00333 moles
1 mol = 6.022 $\times$ 10²³ molecules
0.00333 moles = 0.00333$\times$6.022 $\times$ 10²³ molecules
= 0.02 $\times$ 10 ²³ molecules
Hence, 0.06 g of water has 0.02 $\times$ 10 ²³ molecules