Thermochemistry

Activity 3B:When 100 cm3 of 2.0 mol dm−3 of dilute hydrochloric acid, HCl is added to 100 cm3 of 2.0 mol dm−3 of sodium hydroxide, NaOH solution, the temperature of the reaction increases from 30.0 °C to 43.5 °C.[Specific heat capacity of solution, c = 4.2 J g−1 °C−1; density of solution = 1 g … Read more

Experiment 3A (Comparing Heat of Neutralisation):Aim: To determine and compare heat of neutralisation between acids and alkalis of different strengths. A. Reactions between a strong acid and a strong alkali, and a weak acid with a strong alkali.Problem statement: Does the reaction between a strong acid and a strong alkali produce a higher heat of … Read more

Activity 3A:A student carried out an experiment to determine the heat of displacement for the reaction between copper, Cu and silver nitrate, AgNO3 solution. In this experiment, excess copper powder, Cu is added into 100 cm3 of 0.5 mol dm−3 of silver nitrate, AgNO3 solution.The heat of displacement in this experiment is -105 kJ mol−1.[Specific … Read more

Laboratory Activity 3C (Determining Heat of Displacement):Aim: To determine and compare the heat of displacement of copper from copper(II) sulphate, CuSO4 solution with zinc metal, Zn and magnesium metal, Mg.Materials: 0.5 mol dm−3 of copper(II) sulphate, CuSO4 solution, magnesium powder, Mg and zinc powder, Zn.Apparatus: Polystyrene cups with lids, thermometer, measuring cylinder and spatula.Procedure:1. Based … Read more

Laboratory Activity 3B (Determining Heat of Precipitation):Aim: To determine the heat of precipitation of silver chloride, AgCl and magnesium carbonate, MgCO3.Materials: 0.5 mol dm−3 of silver nitrate, AgNO3 solution, 0.5 mol dm−3 of sodium chloride, NaCl solution, 0.5 mol dm−3 of magnesium nitrate, Mg(NO3)2 solution and 0.5 mol dm−3 of sodium carbonate, Na2CO3 solution.Apparatus: Two … Read more

Question 1:The thermochemical equation for the decomposition reaction of calcium carbonate, CaCO3 is as follows:(a) Draw the energy level diagram for the reaction.(b) Write three statements that can be obtained from the energy level diagram in (a). Answer:(a)(b) 1. The decomposition of calcium carbonate, CaCO3 is an endothermic reaction.2. When 1 mole of calcium carbonate, … Read more

Laboratory Activity 3A (Determining Exothermic and Endothermic Reactions):Aim: To study the types of reactions based on heat change and the changes in thermometer readings when substances dissolve in water.Materials: Solid sodium hydroxide, NaOH, solid anhydrous calcium chloride, CaCl2, solid ammonium nitrate, NH4NO3, solid sodium thiosulphate, Na2S2O3 and distilled water.Apparatus: Polystyrene cups with lids, spatula, measuring … Read more

Comparison of Combustion Heat of Difference Fuel The table below shows the heat of combustion of a few fuel. It shows that when the number of carbon in a molecule increase, the heat of combustion will increase. Alcohol MolecularFormula DH (kJ mol-1) Methanol CH3OH ‑715 Ethanol C2H5OH ‑1376 Propan-1-ol C3H7OH ‑2017 Butan-1-ol C4H9OH ‑2675 If … Read more

Combustion Combustion is a reaction when a substance burns completely in the excess oxygen. Example, combustion of methane in excess of oxygen produces carbon dioxide and water.CH4 + 2O2 → CO2 + 2H2O All fuel combustion are exothermic reactions. Heat of Combustion The Heat of Combustion of a substance is the heat energy released when 1 … Read more

The heat of neutralisation is the heat energy evolved when an acid reacts with a base, per mole of the acid or base. All measurements are made under standard state conditions. An example of the enthalpy change of neutralisation is the heat change obtained in the reaction between sodium hydroxide and hydrochloric acid. The equation … Read more