Sodium Thiosulphate & Acid :: GCSE Chemistry Coursework Investigation

Sodium Thiosulphate & Acid Planning To ensure that this experiment is safe, I have taken some precautions. I wore goggles at all times, made sure not to spill any chemicals such as the acid onto skin or clothes, and to be aware of glass. I have used various different apparatus, including two measuring cylinders, one 25ml, and the other 50ml. I used a 150ml chronicle flask and a stopwatch. Here is a few diagrams of these apparatus. What I Will Vary, Not Change To Keep A Fair Test & What I Will Observe & Measure I will vary the amount of Sodium Thiosulphate (10-50ml), but keeping the same amount of Hydrochloric Acid (25ml) to make it a fair test. Also when I vary the amount of Sodium Thiosulphate, I will always keep the same total volume of the mixture, therefore topping it up to 75ml every time. I will be observing the reaction of the two chemicals, and measure how quickly the sulphur is produced. I will also keep the start temperature the same. What Will I Try To Find Out I am going to find out how long it takes for Sodium Thiosulphate ( ) to react wit Hydrochloric Acid (HCL) to produce Sulphur so you can no longer see through it (opaque). To do this I will use paper with writing on, and wait until I can no longer read it, because the solution will turn 'milky.' My Prediction The stronger the solution, therefore the more Thiosulphate particles, the quicker the reaction because; there will be more particles in the solution to react with the Hydrochloric Acid, with a bigger percentage chance of reacting/hitting it. This is because if there is more particles in the total substance of 75ml, there is less surface area free. Twice the amount of particles, in the same total volume, means twice the chance of collision therefore in theory half the time on reaction, due to a high concentration. This is the 'Collision Theory.' This means that my overall prediction is that when the strongest amount of Sodium Thiosulphate is added to the Hydrochloric Acid, it will react faster. This also, proved above means that I will not need to add water, so preventing dilution. Diagram Proving Prediction Method 1. Measure out 25ml of Hydrochloric Acid (Hcl) - keep the same every time. 2. Measure out the needed amount of Sodium Thiosulphate ( ) in a cylinder 3. Pour ( ) into a chronicle flask 4. Place paper with writing on under flask 5. Add Hcl, as soon as it mixes with the ( ), start the stopwatch 6. As soon as the solute has finished reacting, and the writing is no