Question

How to calculate the number of molecules in 18g of H2O

Answer 1

We, know molecular mass of water is, M = 16 g/mol .

Given mass of water, m = 18 g.

We know, number of moles is given by :

$n = \dfrac{18\ g}{16 \ g/mol}\\\\n = 1.125\ moles$

Now, 1 mole of any compound contains 6.022 × 10²³ molecules.

So, number of moles in 1.125 moles of water is 1.125 × 6.022 × 10²³ =

6.77 × 10²³ molecules.

Hence, this is the required solution.