1. Fix the data logger so that it records for a time of 300s, with 1 sample per second. 2. Connect the thermometer to the data logger, and have it fixed, ready to use. 3. Place in one beaker (clean and dry) 180 ml of distilled water. Put the electronic thermometer inside the beaker and start recording for 120 seconds. 4. Weigh 5.4g of ammonium chloride, and place it in the beaker with the distilled water after the 120 seconds are recorded. Stir and leave it for 180 seconds. Save your results, organize them in the pc, and produce a graph of temperature against time.
5. Repeat steps 2-4 and produce an average temperature for this solution, as well as a graph of time against average temperature. Make sure to clean and dry the beaker prior to repeating the experiment; this way the test will be fair. 6. From the average temperature, determine ?T (numerical difference before/after the addition of the solute), and do the process for calculating the enthalpy change. Part B 1. Now, take a clean and dry beaker, and place 48ml of distilled water inside. Put the electronic thermometer inside and start recording with the data logger, for a period of 120 seconds. 2. After that period of time, weigh and place 1.6 g of Iron Chloride inside the beaker. Stir it well, and leave it for 180 seconds more.
3. Repeat steps 1-2 again, make sure to have a clean and dry beaker for repetitions. 4. Produce an average temperature produce an average temperature for this solution, as well as a graph of time against average temperature. Make sure to clean and dry the beaker prior to repeating the experiment; this way the test will be fair. 5. From the average temperature, determine ?T (numerical difference before/after the addition of the solute), and do the process for calculating enthalpy change. 6. Process, compare, and analyze the results between the two solutions.
In this experiment, it was evidenced how exothermic and endothermic reactions take place. Endothermic reactions, refers to those chemical reactions that must absorb energy in order to carried. On the other hand, exothermic reactions are those which release thermal energy from a chemical reaction. Throughout the experiment various procedures were followed in order to obtain the demonstrated data; the crucial part, is to measure quantities in its correct amounts. This is important, as the number of moles between the solute and the solvent must be equal to a ratio of 1:100, very common when referring to aqueous equations.
Therefore, when doing calculations, numbers should not be rounded until the final answer. That day, the accuracy will not be lost, and the ratio between solute and solvent is going to be viewed correctly. In order to make theorems occur in experiments, there must be extreme accuracy in all aspects. An aspect that should be carefully seen is the mass of substances. Some groups did not use electronic scales, and used manual scales; that means that the normal error is greater.
The electronic scale has an error of 0.01, while the electronic scale has an initial ï¿½0.1 plus usual human mistakes or laziness for precision. When calculating the enthalpy change for iron chloride, there was a small uncertainty as the ratio of the solute did not match the solvent one. In those cases, the most reliable thing to do is divide the number of moles of the solvent by 100 and follow what the theoretical procedure says. The possible cause for this could have been an imprecision when measuring quantities, therefore those mistakes appeared.
Although one could say that electronic measurements are accurate, it was evidenced that between trials, differences were noticed. Therefore, it is best to do more than two in order to obtain the best average possible. One discrepancy noticed, was the measuring of liquids. These were not measured by electronic means, while the powders were. This means that measurements can slightly change, as one measuring instrument is manual and one is electronic.
This makes that the experiment looses its fairness, and thus the experiment will not be correctly done. For future occasions, it is best to measure all with electronic instruments, preferable of the same brand so that the error margins reduce. Further, in order to have a proper reading of the graphs, all solutes should be inserted into the solvent at 120 seconds. Some groups did not care about this issue.
This is an important step, as results can be easily seen, and secondly because if the experiment wants to be fair, all substances should be left with the same time for reaction. Some groups poured the solute at 135 seconds, because they were not ready; this made the experiment a bit inaccurate. For future occasions, it is best to have everything in hand 10 seconds prior to the 120 seconds margin, and thus the laboratory will increase its accuracy.