Experimental Determination of the Rate of Reaction

AQA A-level ChemistryRate of ReactionLesson 3 of 11

Titrations can be used to work out the concentration of reactants or products as the reaction progresses. Samples (aliquots) of the reaction mixture are taken at intervals for titrations to determine the concentrations. The reactions in the samples must be quenched (stopped) before the titrations. This is done by adding the sample to ice-cold water. Colorimetry uses a colorimeter or a spectrophotometer to measure the amount of light of a particular frequency (colour) absorbed. The more concentrated the solution the more light is absorbed. Change in Mass can be used if a gas is evolved during a reaction. The reaction vessel is placed on a balance and weighed at regular intervals. Volume of Gas Evolved can be measured at regular time intervals if a gas is produced. The volume of gas is proportional to the moles of gas and therefore the concentration. The change in electrical conductivity and pH Changes can be measured as the reaction progresses. The time for a reaction to finish or for a precipitate to appear can also be measured. The reactant not being investigated must be in a large excess.

More in Rate of Reaction

• The Rate of a Reaction
• Measuring Reaction Rates
• The Rate Equation
• The Order of a Reaction
• The Rate Constant k
• Worked Example
• Half-Lives and Reaction Rate Graphs
• The Rate Determining Step

All 11 lessons in Rate of Reaction · All AQA A-level Chemistry topics