# What is the smallest entity of a hydrate (e.g. CuSO4 • 5H2O)? (A formula unit?)

$C u S {O}_{4} \cdot 5 {H}_{2} O$
Copper sulfate is a white powder. It may be recrystallized from water to give the pentahydrate, which has a truly beautiful blue colour. Macroscopic crystals of the hydrate may be grown, and the formula of this material corresponds to the given $\text{pentahydrate}$.