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Finding the enthalpy of decomposition of Sodium Hydrogencarbonate

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Introduction

Chemistry Coursework Finding the enthalpy of decomposition of Sodium Hydrogencarbonate IMPLEMENTING PART ONE: THE REACTION OF SODIUM CARBONATE WITH HYDROCHLORIC ACID I decided to add 2.76g of sodium carbonate to the hydrochloric acid solution at the fourth minute, consequently there is no result for this time in my result's table that follows- (The start temperature of the acid was 20.5�C) TIME (MINUTES) TEMPERATURE (�C) 0 20.5 3 20.4 Na2CO3 ADDED - 5 26.6 6 26.6 7 26.6 8 26.4 9 26.2 10 26.0 PART TWO: THE REACTION OF SODIUM HYDROCARBONATE WITH HYDROCHLORIC ACID I decided to add 3.65g of sodium hydrogencarbonate to the hydrochloric acid solution at the fourth minute, consequently there is no result for this time in my result's table that follows- (The start temperature of the acid was 20.5�C) TIME (MINUTES) TEMPERATURE (�C) 0 20.5 3 20.4 NaHCO3 ADDED - 5 11.8 6 11.8 7 12.0 8 12.1 9 12.3 10 12.4 In order to find the exact change in temperature for each part of the experiment I will have to draw a graph and extrapolate back from my line of best fit for each set of results. ANALYSIS If I assume that the relative formula mass (Mr) ...read more.

Middle

tried to keep my results as accurate and reliable as possible by doing things such as washing the thermometer after taking the temperature, and stirring the mixture for the same amount of time before taking each reading. I also recorded the temperature of the acid and alkali before starting the experiment (these values are shown in my results table) this made sure that they where the same temperature and therefore made my experiment more reliable. However there where errors that I could not do anything about. These are percentage errors and every piece of equipment has them. In order to see how accurate my experiment was I am going to calculate the main percentage errors. These are for the measuring cylinder, the thermometer, the graduated flask, the balance and then the overall percentage error. For the measuring cylinder it is: 0.5 x 100 50 = 1.0 % for the thermometer: 0.1 x 100 4.6 = 2.17 % For the graduated flask: 0.125 x 100 250 = 0.05 % For the balance: 0.01 x 100 12.33 = 0.08 % My overall percentage error is: 1.0 + 2.17 + 0.05 + 0.08 = 3.30 % As you can see from my calculations my experiment was not very accurate in a number of places. ...read more.

Conclusion

To reduce this error if I did the experiment again I would use a burette or a graduated pipette, as these pieces of equipment are more accurate and therefore the percentage error would be reduced making my experiment more accurate and reliable. To make my experiment even more reliable I could do repeat experiments and then take an average value for my enthalpy change from these results. This would also indicate to me how accurate I had been while conducting the experiments as close repeat results would indicate that I had been accurate and reliable. My experimental result is also lower than the actual enthalpy change as my apparatus lost vast amounts of heat as they had no insulation of any kind. This made my overall enthalpy change -38.99kJ mol which would mean an acid similar to HCN was used in the experiment when actually I think that the enthalpy change should have been nearer -57 kJ mol and the acid used was probably more like citric acid. Finally to improve the results, if I conducted the experiment again, I would use data logging to gather my results so that they would be more reliable as a computer would be reading the temperature not a person so no human errors would occur in gathering the results. Jennifer Meakin ...read more.

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