Unit 3 Chemistry SAC 1: Calorimetry Comparison and Evaluation task for AOS 1 Scope and sequence Two experiments to be performed during Week 3 - results recorded in log books. Week 4: Set of questions relating to the data collected sat under test conditions. Time for questions: 60 minutes Data book allowed Logbook needed to record answers and to show results. Marking: Marks are totalled from · a clear record of your measurements · calculations derived from your measurements · the assessment questions Topics covered · calibration and use of calorimeters · thermochemical equations and calculations. (Ch 3 Pearson) PTO
Unit 3: SAC 1 - Calorimetry (comparison and evaluation of data) Part A: Heat of combustion of alcohols Aim: To determine and compare the heats of combustion of alcohols. Method Add 100 g of water to a steel can (or 250 ml beaker) Sit the can on a pipe clay triangle on a tripod or hold the can in a retort stand. Record the temperature of the water. Weigh an ethanol burner. Light the burner and place it under the steel can. Burn for 5.00 minutes. Record the temperature. Record the final mass of the ethanol burner. Other groups will use different alcohols and data will be shared. Measurements (record your measurements in your logbook) 3 marks Part B: Heat of solution of NH4Cl (comparing calibration methods) Aim: To determine the heat of solution of NH4Cl using three different methods. Method Add 80 g of water to the calorimeter. Record the temperature. Weigh 5 g of NH4Cl. Add the NH4Cl, stir and record the temperature change. Calibration method 1 - chemical calibration Replace the 80 g of water and record the temperature. Weigh 5 g of NaOH solid. (heat of solution of NaOH 44.5 kJ) Add the NaOH, stir and record the temperature change. Calibration method 2 - electrical calibration Replace the 80 g of water and record the temperature. Add a power supply and ammeter to the circuit. Add a voltmeter in parallel. Get the teacher to check your circuit. Run the current for 4 minutes, recording the temperature every 30 secs. Measurements 6 marks
Unit 3: SAC 1 Your logbook should show · your measurements · your calculations of ??. Part A 1. Write a balanced equation for a. the complete combustion of propanol. 2 marks b. the incomplete combustion of ethanol. 2 marks 2. Draw an energy profile diagram on the grid provided for the combustion of ethanol (use the first row of the table that was on the board). The activation energy is 220 kJ 2 marks 3. a. What conclusion can you draw about the significance of the height of the burner? 2 marks b. How could you determine the ideal height to place the burner? 4. a. Cut out the grid attached and use it to graph the heat of combustion of the three alcohols. 4 marks b. What conclusion can you draw about the fuels? c. Why do they have different AH values