Sodium thiosulphate solution react with dilute sulphuric acid to form a yellow precipitate of sulphur. In this experiment, the time taken for the formation of sulphur to cover the mark 'X' until it disappears from sight can be used to measure rate of reaction.
As the concentration of sulphuric acid is increased, the rate of reaction between sulphuric acid and sodium thiosulphate increases.
Explanation using collision theory
· When the concentration of the solution of a reactant increases, the number of particles per unit volume of the solution also increases.
· With more particles per unit volume of the solution of the reactant, the frequency of collision increases.
· This causes the frequency of effective collision to increase. Hence, the rate of reaction increases.