The effect of changing concentration of sodium thiosulphate on the rate of reaction between sodium thiosulphate and hydrochloric acid.

Fair test- we can make this experiment a fair test by keeping the overall volume of the solution the same. The amount of acid going into the solution remains constant throughout the whole experiment. We have two variables, they are the volume of water and the volume of sodiumthiosulphate. The reason we have chosen the water and the sodiumthiosulphate to be the variables is this way we can change the concentration of sodiumthiosulphate.

Diagram:

Results

Method

• Get out equipment, the equipment needed is:12 test tubes, a chlonical flask, 3 measuring cylinders, a white tile and a cross, 220cm3 of sodiumthiosulphate, 60cm3 of hydrochloric acid, 150cm3 of water.
• Place chonical flask on cross which is on the white tile.
• Pour 10cm3 of hydrochloric acid into a test tube.(you only need 10cm3 for each experiment)
• Pour required amount of sodium thiosulphate into a measuring cylinder for the first experiment you will need 60cm3 or thiosulphate, for the second you will need 50cm3, for the third you will need 40cm3, for the fourth you will need 30cm3, for the fifth you will need 20cm3 and for the sixth you will need 10cm3
• Pour the required amount of water into a measuring cylinder. for the first experiment you will need o cm3 of water, for the second you will need 10cm3, for the third you will need 20 cm3, for the fourth you will need 30 cm3, for the fifth you will need 40cm3 and for the sixth you will need 50cm3 or water.
• Pour the water and the sodium thiosulphate into the chlonical flask.
• Then pour in the 10cm3 of acid. (note this must always be added after the sodiumthiosulphate)

Analysis

I believe that this experiment was not totally accurate, the reason for this is because we were measuring the time it took for the cross to disappear with our eyes. We could have made this experiment more accurate by using an electronic device, we would’ve put a light under the chlonical flask and had a light sensor above it. When no light passed through it, it meant that the two chemicals had reacted together. In my experiment I believe that my anomalies were caused because we were measuring with our eyes. The anomalies in my experiment, were only a few seconds out. Although measuring the time taken for the cross to disappear using my eye was quite accurate, unfortunately it was not accurate enough. I could’ve made the experiment more accurate if we were measuring using our eyes, we could have done more than just two experiment, but three or four, then taken the average. On my graph m results were a curved line this means that the rate of which the reaction took place slowed down as the concentration of the sodiumthiosulphate was decrease. The only thing that went wrong with my experiment was that the results were not as accurate as they might have been if they were done using electronic equipment or doing more experiments.

Conclusion- when I predicted that the rate of which the sodiumthiosulphate would react with the hydrochloric acid I predicted that it would increase as the concentration was increased. This is because the higher the concentration of thiosulphate the more the particles will collide into each other and create a chemical reaction, the more they bump into each other, the faster and the greater the chemical reaction will be. The chemical equation for the experiment is this:

Sodiumthiosulphate + hydrochloric acid = sald+water+so2+s