percent concentration

Concentration says how much solute (the substance dissolved) is packed into a given amount of solution (solute plus solvent together). The everyday form is percent concentration (mass of solute per volume of solution): divide the solute by the whole solution and multiply by 100. Dissolving 5 g of salt to make 100 mL of solution gives (5 ÷ 100) × 100 = 5%, meaning 5 g in every 100 mL. To find an amount instead, take the percent over 100 and multiply by the volume: a 20% solution in 150 mL holds (20 ÷ 100) × 150 = 30 g. The classic error is to divide by the solvent instead of the whole solution, or to forget the × 100 and leave a decimal like 0.05 where a percent was asked. Concentrations can be lowered by dilution.