In this project, I am trying to assess the effect of concentration of sodium thiosulphate in the acid/sodium thiosulphate reaction as follows: – Sodium thiosulphate + hydrochloric acid ==>Sodium Chloride + Sulphur + Sulphur dioxide + water Or Na2S2O3+2HCl ==>2NaCl + S + SO2 + H20 Some of these chemicals are hazardous unless handled correctly – here is a safety table of the substances I am using:- Chemical Hazard Procedure Sodium Thiosulphate – Na2S2O3  Harmful if ingested in quantity In reactions with acid – Sulphure dioxide is produced. Ventilate room Hydrochloric Acid – Hcl  Corrosive  Irritant.

May cause burns  Vapour is very irritating to the respiratory system  Wear protective clothing  Ventilate room Sulphur Dioxide – SO2  Irritant to respiratory system  Noctious gas  Ventilate room Sodium Chloride – NaCl Irritant  Harmful if ingested in quantity  If contact with skin occurs, wash thorugly. Sulphur – S NO HAZARD N/A Water – H20 NO HAZARD N/A To do this I am attempting to measure the speed (time period) in which it takes the colloidal effects of the reaction to reduce visibility of a black cross marked underneath. In order to start the experiment, I will need the following apparatus: -Conical flask  10ml + 100ml Measuring cylinders  A4 paper (white) .

Black Marker Pen  Sodium Thiosulphater  Stopwatch Here is a diagram of the proposed experiment: Preliminary Experiment In my preliminary experiment I found that is was necessary to keep that cross the same, as it would change the accuracy of results. Also, that using a ratio of each, increasing in graduations of 10 would not provide enough results for a conclusion. These were my preliminary results: – Concentration (M) Na2S2O3 (ml) H2O (ml).

Time (s) Method I am going to attempt to calculate the effects of concentration on the acid/sodium thiosulphate reaction by first filling the flask with 5mls of 2M hydrochloric acid. I will then add a mixture of water and sodium thiosulphate to the mixture these ratios of each: – Water: Sodium Thiosulphate  0:50ml 5:45ml  10:40ml 15:35ml  20:30ml  25:25ml 30:20ml  35:15ml  40:10ml  45:5ml This makes 50mls of additional liquid to add. I will then time how long it takes for the reaction to take place once they are mixed.

I will start the stopwatch when the water/sodium thiosulphate is poured totally into the flask with the acid, and stop the timer when the cross is no longer distinguishable from view due to the opacity of the liquid in the flask. It will be a fair test as I am using the same amount and concentration of acid and only varying the concentration of sodium thiosulphate.

The amount of liquid in the flask will stay the same as I am not changing the volumes and I am also keeping the cross the same thickness and size. I have decided to apply the same changes to each flask e. g.shaking the flask to encourage colloidal formation. The temperature during the experiment will be at the current room temperature, which may vary slightly, but so little that this will not effect the experiment (approx. 1-3oc).

The same person will always look at the cross to ensure consistency when observing. I am choosing to use measuring cylinders to measure liquid volumes in this experiment as I feel beakers are too inaccurate and none of the small size required are available. Measuring cylinders are the right size, and have appropriate intervals between markings to allow precision when using the liquids.