Graph of an experiment performed to study the effect of the concentration of the reactants on the rate of the reaction. The experiment placed magnesium ribbon in dilute (one molar) and concentrated (four molar) hydrochloric acid. The volume of hydrogen gas produced by each reaction was measured over ten minutes. In dilute acid (blue line) hydrogen is produced gradually, but it is clearly seen that the gas is produced much more quickly in concentrated acid (red line). This is because concentrated acid has more hydrogen ions in a given volume that can attack the magnesium.