1. Data Collection (2 points) Observed Melting Point Rangel\"C) Begins to liquef
ID: 547947 • Letter: 1
Question
1. Data Collection (2 points) Observed Melting Point Rangel"C) Begins to liquefy Completely liquefied (use any reference material) Literature Melting Point ( Compound Acetanilide 111-110 114.3 Recrystallization Acetanilide ( Extractiorn Benzoic acid Extraction 110-114 114.3 120-123 122.4 p-Chloroaniline Extraction 32-6 72.5 1) Compare the melting points of your samples with the literature melting points. Comment on purity of the samples. (1 point 2) Comment on the discrepancy (f exists) in melting points for the two acetanilide samples. u point)Explanation / Answer
1)
Melting point is the temperature at which solid sample melts. Pure compounds have sharp and distinct melting points. Presence of impurities results in lowering of melting point.
Literature melting point of acetanilide sample is 114.3oC. Observed melting point of recrystallized acetanilide sample is 111-116oC. The observed melting point range is very wide (spread over 5oC), indicating presence of slight impurity or use of excess sample for determining melting point.
Observed melting point of acetanilide obtained after extraction is 110 – 114oC. The lowering of boiling point can be attributed to presence of impurities in the sample.
Literature melting point of benzoic acid is 122.4oC. Observed melting point of benzoic acid obtained from extraction is 120-123oC. Slight decrease in melting point may be attributed to traces of impurities. Thus, benzoic acid obtained after extraction is pure and contains only traces of impurity.
Literature melting point of p-chloroaniline is 72.5oC. Observed melting point of p-chloroaniline obtained after extraction is 62-68oC. Observed melting point is considerably less than expected melting point. Thus, sample of p-chloroanline is significantly impure.
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2)
Acetanilide obtained after extraction has melting point of 110-114oC. Melting point of recrystallized acetanilide is 111-116oC. There is slight discrepancy in the melting point. The extracted acetanilide starts melting slightly lower temperature indicating presence of some impurity. Recrystallized sample on the other hand show a wider range indicating use of larger amount of sample for determination of melting point or presence of trace level of impurities even after recrystallization.
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