An increase in temperature will generally lead to an increase in the rate of reaction. While a decrease in temperature will lead to a decrease in the reaction rate.

This is because increasing the temperature of the reaction supplies enough kinetic energy to the reactant particles making them to move faster making more effective collisions per unit time. Hence the reaction rate also increases. On the other hand decreasing the temperature will make the reactant particle to move at a slow speed and hence will make few effective collisions leading to a decrease in the reaction rate.

• Experimental investigation of the effect of temperature on rate of reaction

Example

Reaction between sodium thiosulphate solution and hydrochloric acid

Requirements

Sodium thiosulphate, hydrochloric acid 100cm3 beaker or conical flask, a piece of white paper, a stop-watch.

Procedure

Measure 30Cm³ of 0.05M sodium thiosulphate solution into a beaker at 25°C and place the beaker on the cross marked on the white piece of paper. Add 25Cm³ of 2.0M hydrochloric acid and immediately start the stop-watch, Stop the clock as soon as the cross cannot be seen. The time taken for the cross to disappear is noted.

Repeat the experiment at 30°C, and 40°C, respectively using the same volumes and concentrations of the sodium thiosulphate and hydrochloric acid solutions,

Observation

As temperature increases, the time taken for the cross to disappear becomes shorter.

Conclusion

The higher the temperature, the faster the rate of reaction. Therefore, rate of reaction is dependent on the temperature.