Rates of Reaction Investigation

Measuring Cylinder

Small measuring cylinder

Flask

2 beakers

Pad (marked with black cross) white cross

Timer

Plan and Method

To investigate what effect concentration of sodium thiosulphate has on the rate of reaction. The volume of HCL needs to be kept at 10cm3 constantly each time. Start with 60cm3 of sodium thiosulphate. Last reaction will have only 10cm3 of sodium thiosulphate.

Reactions will be completed when the x disappears, for the timing to stop. Three reactions will be made for each test; this is done to gain the different averages.

Collect all the apparatus and set them all up. Light the Bunsen burner and fill a beaker with 100 ml of water, then measure 20ml in a measuring cylinder and put into a conical flask. Put the conical flask in with the beaker. Keep checking the temperature by using thermometer. When it gets to the wanted temperature, take the conical flask out and put it on the piece of paper with the cross on it. Add 20ml of hydrochloric acid then start the stop-clock. You then have to wait for the mixture in the flask to go a cloudy colour so you cannot see the cross on the piece of paper. Once it has done this stop the stop-clock and make note of the time. This is then done for the rest of the temperatures.

This will be made a fair test by not stirring the hydrochloric acid and do the exact same procedure to the other tests.

Results

Temperature

Time Taken

Taken

20°C

31.16 seconds

30°C

82.63 seconds

40°C

31.02 seconds

50°C

31.16 seconds

60°C

24.55 seconds

70°C

5.95 seconds

Conclusion

The experiments made were very successful and we had managed to complete the experiment fully and fairly.

My results show that the higher the temperature the less time it takes to go a cloudy colour. This is because the hot particles in the water react quicker when they are hot. The particles bounce off each other which make reactions act quicker. If you didn't use a Bunsen burner to heat the water up the process would take much longer.

My prediction was:

"The higher the temperature, the less time it will take to go cloudy"

I found out that this was true.

Improvements

The experiments were handled fairly but it could have been even fairer because the reaction was finished when the black cross on the pad disappeared and this is only seen by the naked eye. With the whole class doing this with different eye types, there is no exact fairness in the experiment.

Fairness in this issue can be found by using devices such as a light sensor. The light sensor will pass through the flask, of were the reaction is taking place to a receiver. When the light sensor can not reach the receiver, the timing will be stopped automatically. This will bring fairness to experiments to test all similar to rate of reaction.