4.15 describe experiments to investigate the effects of changes in surface area of a solid, concentration of solutions, temperature and the use of a catalyst on the rate of a reaction

4.15 •surface area: 1.put a set mass of marble chips in hydrochloric acid

                               2.time the reaction in regular intervals 

                               3.crush the calcium carbonate further down 

                               4.time again and compare

                  •the more surface area (the smaller the pieces), the faster the reaction 

                  •the extra surface area gives a quicker reaction and there is also more gas evolved overall (as long as the acid is in excess)

     

          •concentration: 1.react magnesium metal with dilute hydrochloric acid 

                                   2.this reaction gives off hydrogen gas, which we can measure with a mass balance as shown

                                  3.time at regular intervals 

                                  4.increase the concentration of acid, keeping the amount of magnesium and volume the same 

                                             •you can use the gas syringe method above 

                    •the higher the concentration, the faster the reaction 

          •temperature: 1.add sodium thiosulphate and HCL (both clear), which form a yellow precipitate of sulphur 

                                 2.time how long the black mark disappears at each temperature 

                                 3.repeat at different temperatures 

                   •the higher the temperatures the quicker the reaction 

                              •you can use this for concentrations 

                              •there is no set graph for this  

          •catalyst: 1.sprinkle manganese(IV) oxide catalyst to hydrogen peroxide 

                         2.hydrogen peroxide given of oxygen gas and the water is left behind 

                                    •oxygen gas moves the gas syringe and you can time how long it takes

                   •the better the catalysts, the faster the reaction 

                             •this reaction can be used to measure the effects of temperature or of the concentration (it will look the same as parts 1 + 2)