Dependence of the reaction velocity on the concentration (Landolt reaction)

Principle

The reaction rate is of a chemical reaction depends on the reaction temperature and the concentration of the reacting substances. The concentration of the starting materials is one of the essential influencing variables on the reaction rate.

In general the higher the concentration of the starting materials is, the faster the corresponding reaction takes place. For simple reactions (first order reaction) the reaction time is inversely proportional to the concentration of the starting material. In this experiment the students investigate the reaction rate of the so-called Landolt reaction at different concentrations of the starting materials.

In general the Landolt reaction is the time-delayed formation of iodine from iodic acid and sulfurous acid. The students observe that (as a rule) a reaction rate is higher if the substance concentration of the starting materials increases. On the basis of theexperimental results, students recognize that there is a direct relationship between concentration and reaction reate. If the concentration of the starting materials is halved, the reaction time is about twice as long.

Learning objectives

• Landolt reaction
• reaction rate
• reaction rate depends on concentration of reactants