Background information
Sodium thiosulphate and hydrochloric acid are both colourless liquids, when the two reactants are reacted together they produce sulphur. The sulphur that is produced from the reaction changes the solution to yellow and cloudy, this is a precipitation reaction, where a two solutions react and a solid forms in the solution, the solid is said to precipitate out. Some reactions will occur quickly such as fireworks exploding or an apple slowly turning brown. Sodium thiosulphate and hydrochloric acid react together according to the word equation below.
Hydrochloric acid+sodium thiosulphate->sodium chloride + sulphur dioxide + sulphur + water
Formula
Na2 S2 O3 (aq) + 2Hcl (aq) -> 2Nacl (aq) H2o (L )+ So2 (g )+ S2 (s)
Introduction
This investigation will be carried out in order to discover how the concentration of sodium thiosulphate affects the rate of reaction with hydrochloric acid. This reaction occurs due to successful collisions between particles of reactants. Collision theory helps to explain how a chemical reaction occurs, collision theory states that atoms ions and molecules must collide with each other with the correct orientation and the correct amount of activation energy in order for a reaction to occur, if they do not collide with sufficient activation energy Ea they will just bounce back of each other. The activation energy is the minimum amount of energy required to form an activated complex. An activated complex is the transition state molecule, with some bonds partially broken and new bonds partially formed, it is therefore a temporary arrangement which may form products or break apart to form reactants. Activation energy is needed to break the initial bonds in order for new bonds to form. Increasing the concentration of a reactant accelerates the reactions in which they are involved, to react a particle must first collide, and so increasing the number of