By dissolving 2.92g of sodium chloride in 1dm 3 of water we obtain a solution of sodium chloride with a concentration of 0.05moldm -3 . What if we only require 250cm 3 of solution - how much would we need to weigh out in this case. If we wanted 2dm 3 then we would need twice the mass. If we require a concentration other than 1 mol dm -3 we multiply the molar mass by the value we require. You'll find further notes about titrimetric analysis here.
Gravimetric analysis is covered here.
First we calculate the mass require to give us 0.01 moles of KMnO 4 .