Investigation of the rate of reaction with Sodium Thiosulphate and Hydrochloric Acid
Introduction:
We must produce a piece of coursework investigating the rates of reaction, and the effect different concentrations have on them. The rate of reaction is the rate of loss of a reactant or the rate of formation of a product during a chemical reaction. It is measured by dividing one by the time taken for the reaction to take place. There are five factors which can affect the rate of a reaction, according to the collision theory of reacting particles. These factors are temperature, concentration (of solution), pressure (in gases), surface area (of solid reactants), and catalysts.
We will be investigating only the affect that concentration has on the rate of reaction due to the fact that this is the most practical factor to investigate.
Aim:
We aim to see the effects of a change in concentration on the rate of a reaction between the two following substances:
Sodium Thiosulphate + Hydrochloric Acid
NaSO (aq) + HCl (aq)
Method:
We took a beaker and a piece of paper. On the piece of paper we drew an ‘X’ the size of the bottom of the beaker. We added 25ml of Hydrochloric Acid to the beaker and placed it on the piece of paper. We then added 25ml of different concentrations of Sodium Thiosulphate to a measuring cylinder. We used a stopwatch for each reaction and performed the reactions one by one. With each reaction, we took the piece of paper with the ‘X’ on it and placed it underneath the beaker containing 25ml of Hydrochloric Acid. Next we poured the 25ml of Sodium Thiosulphate (n-molarity concentrate, where ‘n’ is the particular concentration) and started the stopwatch from the moment the two liquids came into contact with one another. One person looked vertically down the beaker and stopped the stopwatch as soon as they could no longer see the ‘X’ on the paper due to the solution becoming opaque. The time was then recorded and put into the results table. We repeated this process four times for the same concentration until we achieved a consistent set of results. An average time was calculated also. We then did the same again for other different concentrations of NaSO.