Question

What does it mean if a solution is concentrated?

Answer 1

It means the quantity of solute is particularly large. How large that is depends on the solution being discussed.

For instance, `"3 M HCl"` is not considered concentrated for laboratory purposes, but we tend to see `"12.06 M"` (`37%` `"w/w"`) `"HCl"` considered concentrated, "reagent-grade" `"HCl"`.

Or, `"1 M H"_2"SO"_4` is not considered concentrated, but we tend to consider `"18 M"` (`~~98%` `"w/w"`) `"H"_2"SO"_4` concentrated.

We denote concentrated solutions as liquids, rather than aqueous, if they were dissolved in water, since the solute has basically become the solvent.