Question

calculate the number of molecules present in 90g water

Answer 1

 6.023 x 1023 molecules * 90/18 = 30.115 x 1023

Answer 2

$\mathbb{ \ \ A\ N\ S\ W\ E\ R\: \: }$

= Avagardo number × Mass of water

= 6.023 × 10²³ × 90/18

= 30.115 × 10²³