化学实验报告

The effect of temperature on reaction on rateBackground informationWhen sodium thiosulphate reacts with hydrochloric acid, a precipitate of sulphur forms. The time taken for a certain amount of is used to measure the reaction rate. The sodium thiosulphate solution can be heated to different temperatures before hydrochloric acid is added, so the effect of increasing temperature can be measured.The effect of temperature increase on this reaction can be predicted using the collision theory. This theory says that for a reaction to occur, particles must collide with a certain minimum energy called the activation energy, E A. When temperature is increased, particles have increased kinetic energy and move around faster. There is therefore an increase in the frequency of collisions.Method1.Measure 10 cm3 of sodium thiosulphate solution and 40 cm3 of water into a conical flask.2.Measure 5 cm3 of dilute hydrochloric acid in a 10 cm3 measuring cylinder.3.Warm the thiosulphate solution in the flask to the required temperature.4.Put the conical flask over a piece of paper with a cross drawn on it.5.Add the acid and start timing. Swirl the flask to mix the contents. Take the initial temperature of the mixtureand record it in a table like the one below.6.Repeat the experiment using different temperatures in the range 15o C to 65o C. Remember that one of yourexperiments can be carried out at room temperature and so will not require heating.7.Look down on the cross from above. When the cross disappears, stop timing and note the time taken.Record the final temperature of the mixture of the mixture in the flask.8.Immediately wash the solution down a sink with plenty of water.ResultsAnalysisWhen there is higher temperature, kinetic energy of particles will be larger results in:●Particles moving around more quickly which increases the frequency of collisions●The proportion of successful collisions increases because the proportion of particles exceeding theactivation energy increases.ConclusionThe rate of reaction increases with the temperature increases.Future workChanging different temperature more times and calculate rate of reaction.Enthalpy of Reaction (Neutralization)Background informationWe are going to investigate the enthalpy of neutralization for the reaction between solutions of sulphuric acid and sodium hydroxide.The enthalpy change of neutralization of an acid is defined as the enthalpy change when an acid and a base in dilute aqueous solution react together to form one mole of water:H+ (aq) + OH- (aq) H2O (l)When an acid in solution is neutralized by a solution of sodium hydroxide the reaction is exothermic. The enthalpy change depends on the strength of the acid. Many enthalpy changes can be measured quite simple in the laboratory. We usually do this by arranging for the energy involved in the reaction to be transferred to or from water.4.2J of heat energy are required to raise the temperature of 1 cm3 of the aqueous solution by 1oC (we assume it is the same as pure water). This is known as the specific heat.The heat evolved is therefore calculated using the formula:-q = m x c xΔTWhere: q is the heat energy transferred,c is the specific heat capacity of water (4.2 JK-1g-1)m is the mass of the water, andT is the change in temperature of the water.MethodMethod for experiment I:1. In a measuring cylinder place 40 cm3 of NaOH (1.0 mol dm-3).2. Pour it into the calorimeter provided and note its temperature.3. In another measuring cylinder put 60 cm3 of H2SO4 (0.67 mol dm-3).4. Add the 60 cm3 of H2SO4 to the calorimeter, stir with a thermometer and note the highest temperature reached.Method for Experiment II:1. In a measuring cylinder place 60 cm3 of NaOH (1.0 moles dm-3). Pour it into the calorimeter provided and note its temperature.2.In another measuring cylinder place 40 cm3 of H2SO4 (0.67 moles dm-3).3.Add the 40 cm3 of H2SO4 to the calorimeter, stir with a thermometer and note the highest temperature reached.ResultsFor experiment I:q =m x c xΔT=100 x4.2 x6.5=2730 JFor Experiment II:q =m x c xΔT=100 x4.2 x4.5=1890 JAnalysisIn a chemical reaction:●If the energy needed to break bonds is less than the energy released when new bonds are formed thereaction will release energy and the reaction is exothermic.●If the energy needed to break bonds is more than the energy released when new bonds are formed thereaction will absorb energy and reaction is endothermic.ConclusionEnthalpy change of neutralization is exothermic which released energy to the surroundings, and the more substances react the more enthalpy change there is.Future workChanging different temperature and different amount of substance more times and calculate the enthalpy change.。