To prepare 450 ml of a 30% (w/v) solution of potassium chloride (kcl), how many grams of solute are needed?

The important clue from the problem, would be (w/v). This would indicate that the percent has units of weight per volume. We calculate as follows:

Grams solute =.30 g solute / mL solution (450 mL) = 135 g of solute.

Hope this answers the question. Have a nice day.