Experiment on looking at enthalpy of solutions

Part 2: Looking at enthalpy change between Iron (iii) and distilled water, with a ratio equivalent to 1:100

Calculating enthalpy change for FeCl3+H2O= FeCl3(aq, 100 H2O)

Ratio: (1.6/162.5):(48/18)

Ratio: 0.027:2.7

Q=MCΔT

Q=(48/1000)*4.2*4.3

Q=0.048*4.2*4.3

Q=0.87 Kj

ΔH= 0.87*1/0.027

ΔH=32.2 kj/mol

Conclusion

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 ±0.1 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.

Evaluation

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.