The relationship between the concentration of Sodium Thiosulphate and the reaction rate with Hydrochloric acid :: GCSE Chemistry Coursework Investigation

The relationship between the concentration of Sodium Thiosulphate and the reaction rate with Hydrochloric acid Introduction The rate of reaction is measured by finding the quantity of product made in a certain time. The rate of reaction can be made faster by an increase of temperature, adding a catalyst, increasing concentration or pressure or making the reactants surface area larger. An increase in temperature causes the particles of the reactants to gain more energy and move faster. Collision theory states that this results in more collisions and more of these collisions will have enough energy to cause a reaction. By adding a catalyst the particles will stick to the sides of the catalyst and this increases the rate of reaction. By increasing the surface area there is more surface for the particles to collide with thus causing more collisions and increasing the rate of reaction. Finally by increasing concentration there are more particles moving around in the same space. This equals more reactions, which equals faster rate of reaction. More collisions = faster rate of reaction. In this experiment I shall be investigating the relationship between the concentration of sodium thiosulphate and the rate of its reaction with Hydrochloric acid. The formula for this reaction is: Hydrochloric acid + Sodium thiosulphate>>>>>>> Sodium chloride + Sulphur oxide + Sulphur + water 2HCL(aq)+Na2S2O3(aq)>>>>>>>>>>>>NaCl(aq)+SO 2(g)+S(s)+H2O(l) The reaction is considered to be over when sufficient cloudiness is built up in the reaction flask. This cloudiness is sulphur precipitated from the reactants. This therefore is a precipitation reaction. We are investigating the effect of varying the concentration of Sodium Thiosulphate and not the other variables that can affect rates because: We do not know the right catalyst for this reaction, we are not able to break the reactants down to increase their surface area and we decided not to do temperature because we felt that the most dramatic results would come from concentration. To make this test fair all of these other variables have to remain the same. Hypothesis ---------- I believe that the less concentrated the Sodium Thiosulphate the slower the rate of reaction will be. I say this because the less the concentration the less the amount of particles in the same volume and therefore the less collisions. This means that the rate of reaction will be slower. Plan ---- To obtain our results we will be using the following equipment: Conical flask (To contain the liquids whilst the reaction is taking place.) Pipette (To move reactants and measure out precise amounts.) Goggles (As we are using acid our eyes must be shielded from harmful materials) Apron (To protect the clothes and body. Stopwatch (To count the time taken for the reaction to take place.