Question

What does heating to constant mass mean? What is the purpose of heating to constant mass?

Answer 1

Heating to a constant mass meaning to heat a substance untill the mass of substance remains constant.It is a gravimetric technique in analytical chemistry used to determine the mass of an evolved product relative to the initial mass of unreacted material. The mass of salt is weighed, then heated and measured again after 5-10mins and repeated until the mass doesn't change.
This is important because the mass of the solute needs to be known, but usually there are moleules of water trapped within it and the exact mass isn^,t known. So by doing this water molecules evapourate and what is left behind is the salt itself. helps to findout the actual mass of salt...