Melting Point Experiment

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Discussion The main purpose of the melting point experiment is to determine the melting point of a solid. The melting point of a solid is the initial temperature when a solid starts changing to a liquid and the final temperature when it completely liquefies. The identification of melting point is used as an experimental technic to identify compounds. When a compound is pure the temperature range is sharp, rather than broad that occurs in impure compounds. In this experiment we determined the melting point by heating a small sample of the solid at a fast rate and then at a slow rate. The known compound used to measure the melting point was hippuric acid which has a melting point of 189.5℃. . The results obtained in the fast run was 189.8-197.2℃…show more content…
The first step in this part was to find the melting point of unknown #208. In the first try we did the melting point range was 102.2-137.8. the melting point was determined again in a slow rate because the range obtained in the first try was broad and that was an erroneous result because we are using pure substance, which should have a sharp range. This time the melting point obtained was 128.4-134.7. This time it was not that broad but it was not enough to determine which compound we were using. Finally we did another sloe try and the result was 132.7-134.3, at this point the solid could be either urea or phanacetin. To determine which of the compounds we were working with, the crystals of urea and phenacetin were compared to unknown #208. After these procedures, we determined that the compound being use was phenoceting, in order to prove this we had to use the mix melting technic. For the positive result unknown #208 was mixed with phenacetin and the melting point was 134.2-135.2 and for the negative the unknown was mixed with myristic acid with a melting point of 57.7-113.7. As we can observe the melting point for the negative result was very broad a lower in temperature than the positive result. After all the observations and experimentations, I infer that the unknown #208 is phenocetin. The sources of error in this experiment was that in the second part we could not determine the initial temperature of the compound when the meniscus was forming. Another sources of error could be the size of the sample, too much will increase the mp and maybe broaden. Very little amount will give false results as well (broad) or it might skip the liquid face, go from solid to gas. The heating rate should be kept between 2-4 degrees C faster rate will be a source of error causing the range to be broader and
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