Investigation to find out how the rate of the reaction of hydrochloric acid and sodium thiosulphate solution is affected by the concentration of the sodium thiosulphate

Equipment

• Burette
• Conical flask
• Beaker
• Stopwatch
• Paper with cross marked on it
• Sodium thiosulpate solution
• Hydrochloric acid
• Water

Safety

To conduct my experiment safely I will follow normal laboratory rules, which include:

• The wearing of safety goggles to protect my eyes from chemical splashes.
• Standing up to conduct the experiment, therefore reducing the risk of tripping and spilling chemicals.
• Taking care when handling chemicals, particularly hydrochloric acid and sodium thiosulphate because they are both irritants.  I will not touch my eyes or mouth until I have thoroughly washed my hands.
• Taking care when using glassware to prevent injury.

Fair Testing

   

    In order for my results to be fair and accurate I need to keep a series of things the same in order to obtain the fair results that I need.  They will be:

• I must keep the same amount of hydrochloric acid when testing in order for it to be fair.  I will do this by measuring the exact amount using a burette. I will use 40cm3 and then I will use different amounts of sodium thiosulphate and water but so they add up to the same amount of acid, which is 40cm3
• I will also have to keep the temperature the same as the temperature affects the rate of reaction. I will do this by using a thermometer to measure each chemical.  If the temperature is too high then I will I will put it in cold water. If it is to low I shall put it in hot water. I will have the temperature at 200c

       

Preliminary experiment

   I shall use my experiment to find out which quantities to use I decided to use 8 cms of 2 mol hydrochloric acid and a 0.2 mol of sodium thiosulphate.  I vary the concentration of my sodium thiosulphate.

Results

Conclusion

I have decided to use exactly the same concentrations and quantities in my investigation except I shall repeat the each experiment  3 times

Method

I am going to pour 8 cms of 2 mol hydrochloric acid in to my conical flask I am then going to add my concentrations of 0.2mol sodium thiosulphate. The conical flask shall be placed on the piece of paper with the cross-marked on, as soon as I have a added my concentration of sodium thiosulphate to the hydrochloric acid I shall start the stopwatch. I shall stop the stopwatch when the solution is cloudy enough to prevent me from seeing the cross. I will repeat the experiment again using different concentrations of sodium thiosulphate.  Then to ensure my results are fair I shall repeat each experiment 3 times.

Results

Conclusion

From looking at my results and graph I am able to conclude that the more concentrated the sodium thiosulpate the quicker the reaction. As we look at the graph we can clearly see that if you double the concentration you double the rate   of reaction.                                                                                                                       Before I did the experiments I made some predictions they were that the more concentrated the sodium thiosulphate was the quicker the reaction would happen. This was completely correct because what I thought would happen, did.  My hypotheses was, an investigation to find out how the rate of the reaction of hydrochloric acid and sodium thiosulphate solution is affected by the concentration of the sodium thiosulphate, and I can now answer this as I have found out that the rate of reaction would increase if I increased the concentration and would decrease if I decreased the concentration.

Evaluation

My results are fairly accurate as all of the points lie close to the line of best fit and go through the line of origin, however I feel my results could have been more accurate and I could of repeated ach experiment one more time just to be sure.