How many moles are present in $90 ext{ g}$ of pure water ($H2O$)?

Question

How many moles are present in $90	ext{ g}$ of pure water ($H2O$)?

Accepted Answer

Molar mass of $H2O = 18	ext{ g/mol}$. 
Number of moles $= \frac{	ext{Given mass}}{	ext{Molar mass}} = \frac{90}{18} = 5	ext{ moles}$.

Some Basic Concepts of Chemistry