Crystallising salt solutions

You may be asked to describe how to make a soluble salt.

If the base dissolves in water, you need to add just enough acid to make a neutral solution. Check a small sample with universal indicator paper. If ammonia solution is used, you can add a little more than needed to get a neutral solution.

Warm the salt solution to evaporate the water. You get larger crystals if you evaporate the water slowly.

Copper oxide, and other transition metal oxides or hydroxides, do not dissolve in water. If the base does not dissolve in water, you need an extra step. You add the base to the acid until no more will dissolve and you have some base left over (called an excess). You filter the mixture to remove the excess base, then evaporate the water in the filtrate to leave the salt behind.