Science Coursework
Aim
I aim to investigate how changing the concentration of Hydrochloric acid affects the rate of reaction with Sodium Thiosulphate solution.
Sodium + Hydrochloric Sodium + Water + Sulphur + Sulphur
Thiosulphate Acid Chloride Dioxide
(aq) (aq) (aq) (l) (g) (s)
The reaction makes the solution go a yellow cloudy colour and a gas is given off.
Procedure
To ensure that our results are precise accurate and reliable we are going to take more than one set of results down and we will do the test twice. If there appears to be a set of results that does not fit the pattern we will repeat the test that it occurred in. We will also make sure that the apparatus we are using gives an accurate measurement. Also, in order to keep it a fair test, we will keep all of the variables the same, except from one. This will be the distilled water. We will use the same cross throughout the experiment. Otherwise the shade of the cross could be different so it may take a different period of time for the cross to totally disappear. To ensure that we use the right amount of sodium thiosulphate and the same amount of hydrochloric acid, we will use a pipette. But we must be careful to avoid cross contamination so that the reaction doesn’t take place before we want it to. This will be done by using three different pipettes for the water, sodium thiosulphate and hydrochloric acid. Hydrochloric acid will be the variable in our experiment. We will be using 10ml of sodium thiosulphate and 10ml of hydrochloric acid which will be diluted with distilled water. So we will start with 2ml of hydrochloric acid and 8ml of water. Then 3 ml of acid and 7ml of water. We will carry this on until 10ml of acid and 0ml of water. We will wash out the beaker that is used for the experiment each time a measurement is taken. To perform this experiment I will be using a HB pencil to draw a cross, I will place it under the beaker. The cross disappears as the product of the experiment is cloudy. Using a stopwatch I will measure how long it takes for the mix to go cloudy and then record it in a table of results.
