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Investigation to determine the enthalpy change of formation of magnesium carbonate

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Claire Sommer 6JB Experiment 3A - Investigation to determine the enthalpy change of formation of magnesium carbonate Aim The aim of this investigation is to find out the enthalpy change of formation for magnesium carbonate by thermochemical measurement and using Hess's Law. The enthalpy changes of reaction of magnesium and magnesium carbonate with dilute hydrochloric acid need to be measured. Procedure The reactions between magnesium and hydrochloric acid and magnesium carbonate need to be carried out in separate experiments in insulated calorimeters. After the results are obtained calculations for the heat evolved - including the heat loss to the surroundings and the number of moles need to be worked out. 1) Collect the required apparatus 2) Weigh the weight of the weighing bottle on scales that measure to 0.00 of a gram 3) ...read more.


Then record the temperature of the acid using a temperature graduated to 0.2 degree divisions 7) Add the magnesium to the acid making sure the thermometer is still in the calorimeter and is easy to see. As soon as the two reactants come into contact start the stopwatch 8) At 30 second intervals record the temperature of the reaction until 4 minutes is reached or 240 seconds 9) Take a repeat reading 10) Then weigh the weighing bottle again on the more accurate scales. 11) Then add 3.5g of magnesium carbonate repeating steps 3 and 4 12) Again add 50cm3 of hydrochloric acid to the calorimeter by repeating step 5 13) Record the temperature of the hydrochloric acid 14) ...read more.


Initial temperature - 22.10? Time In degrees Temperature In seconds Time In seconds Temperature In degrees 30 31.10 30 30.40 60 31.00 60 30.25 90 31.00 90 30.10 120 31.40 120 29.95 150 30.85 150 29.70 180 30.65 180 29.70 210 30.60 210 29.70 240 30.60 240 29.20 Conclusion and Evaluation By looking at my results they seem to be fairly accurate as they fit the predicted trend for the experiment. For both tests it is obvious that there are some anomalous results. In the experiment for magnesium for test 1 there is one unusual result. It was 34.00?c for 150seconds when it should have been around the region of 33.70?c. In test 2 the temperature was 29.80 for 240 seconds when it should have perhaps been 29.50?c. For the experiment with magnesium carbonate ...read more.

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