How would you prepare 72.5 g of an aqueous solution that is 5.00% potassium iodide, KI, by mass?
Here's how you can do that.
For starters, you should know that a solution's percent concentration by mass.
In your case, a
Now, you know that the solution must have a total mass of
#72.5 color(red)(cancel(color(black)("g solution"))) * "5.00 g KI"/(100color(red)(cancel(color(black)("g solution")))) = "3.63 g KI"#
You can thus say that the solution can be prepared by dissolving
#"72.5 g " - " 3.63 g" = "68.87 g"#
of water, the solvent.