Write down the dissolution equation for rubidium chromate dissolving in water. (Chromate is a polyatomic ion with the formula CrO42-.) If two moles of the ionic compound are dissolved, then how many moles of the CATION are present in the solution?

Four moles of the cation

Explanation:

2Rb2CrO4(s)<> 4Rb^+(aq) + 2CrO4^2-(aq)

Now looking at the reaction equation, it can be seen that one mole of rubidium chromate contains two moles of rubidium ions and one mole of chromate ions.

The dissolution of two moles of rubidium chromate should then yield four moles of rubidium ions and two moles of chromate ions since the ratio of ions present is 2:1.

This explains the reaction equation written above for the dissolution of two moles of rubidium chromate as shown.