# How would we differentiate calcium chloride, and copper sulfate?

Dissolve a bit of both powders in water. $C u S {O}_{4}$ will give a beautiful blue colour.
$C u S {O}_{4}$ is a white solid (a residue of water will probably give a faint blue colouration). Dissolution in water gives ${\left[C u {\left(O {H}_{2}\right)}_{6}\right]}^{2 +}$, which gives a characteristic blue colour in solution; this is truly one of the most beautiful colours you can see.
On the other hand, calcium chloride, a pure white powder (or colourless crystals) will give a colourless solution. Why the difference in colour? $C {u}^{2 +}$ possesses $d$ electrons, whose transitions give rise to the colour.