Experiment: The rate of reactions and temperature

Aim:  To find the effect of temperature on the rate of reaction: using hydrochloric acid and sodium thiosulphate

Materials: flask, measuring cylinder, stop watch/watch/stop watch app, thermometer with a 0-100°C scale, burner, tripod, sheet of white paper, dilute hydrochloric acid, sodium thiosulphate solution

Methods

1. Mark the sheet of paper with an X
2. Measure out 10cm³  of sodium thiosulphate solution into a flask
3. Add 40 cm³  of distilled water into the solution
4. Warm the solution gently to about 25°C
5. Add 5 of hydrochloric acid
6. Note the temperature and the time
7. Swirl the contents of the flask and place the flask over the X on the paper
8. Observe the X by looking down vertically through the solution
9. Take note of the time it takes for the X to “disappear” i.e. the time it takes for the X to be invisible when viewed through the solution
10. Rinse the flask and repeat the experiment by heating the sodium thiosulphate solution to 30°C,40°C, 50°C and 60°C respectively before adding the acid
11. Tabulate the results
12. Plot the results onto a graph

Observations and results

Rate of reaction and temperature. Image credit bbc

• The higher the temperature of the sodium thiosulphate solution the faster the reaction
• At some point the rate of reaction stops increasing even though the temperature is increased
• This is because at this temperature the particles of the reagents would be colliding at a maximum possible rate i.e the reaction is almost instantaneous/as fast as it can be

Conclusion

• Increasing the temperature of a reaction/reagents results in an increase in the rate of reaction
• This is because as temperature is increased the particles of the reagents move faster and collide at a higer rate
• Also particles can overcome the reaction energy barrier at a faster rate
• This rate cannot be sped up indefinitely at a certain point the rate of reaction stops increasing even though temperature is increased
• This is known as the optimum temperature

To access more topics go to the Combined Science Notes page.