Mixture Melting Points Essay Example

analyzing its melting point. A pure crystalline substance will have a specific range for melting, from the temperature at which crystals begin to liquefy until complete liquid state is achieved. If the mixture is pure, this range will remain consistent. However, the presence of impurities in the mixture causes its melting point to be lower than expected. In other words, a significantly lower measured melting point suggests that the sample is impure due to impurities reducing its melting point.

Experimental

The experimental procedures were obtained from "Introduction to Organic Laboratory Techniques, 4th edition" lab manual. The unknown sample #10 was acquired and its melting point was measured using a melting point apparatus.

Two compounds were selected based on their melting point, which were similar to the unknown compound. Two mixtures were created by combining equal amounts of one potential compound and the unknown #10 using a watch glass. The melting points of all the mixtures were measured using a melting point apparatus. By comparing the melting points of the mixtures, the identity of the unknown compound was determined.

Results and Discussion

The melting point determination showed that unknown #10 had a melting point of 111.5°C. This indicated that dibenzoyl ethylene and o-Toluic acid could potentially be compounds in question, as their melting points closely matched that of the unknown.

After discovering that the melting points of each compound were too similar to the unknown, they decided to combine them for further evaluation. The resulting mixture consisted of dibenzoyl ethylene and the unknown, which exhibited a melting point of 111.2°C. In comparison, the mixture containing o-Toluic acid and the unknown displayed a slightly lower melting point of 109.8°C. By comparing these values

with the melting point of the unknown substance, it was determined that the mixture with dibenzoyl ethylene closely corresponded. This strongly implies that dibenzoyl ethylene is likely to be the unidentified compound due to their close alignment in terms of melting points.

Both the unknown substance and o-Toluic acid, being different substances, caused a decrease in the melting point of the mixture. This decrease was attributed to impurities present in the mixture, illustrating how measuring melting points can determine both purity and identity of a compound.

A potential error during the experiment could have been adding unequal amounts of the unknown and known compounds while combining them. This mistake resulted in inaccurate results, necessitating a repetition of the experiment.

To summarize, this laboratory aimed to identify an unknown sample by using the melting point technique to combine it with possible compounds. Determining melting point is crucial for identifying an unknown substance.

The melting point of an unidentified sample labeled as #10 was determined using a melting point apparatus. The recorded melting point for this sample was 111.5°C. When the unknown sample was mixed with another substance, two possible melting points were observed: 111.2°C and 109.8°C.

Unknown sample #10 can be identified as dibenzoyl ethylene because its melting point is similar to that of the mixture of dibenzoyl ethylene.