Find and report the melting point of 4-nitrophenol, and also the melting point o

Question

Find and report the melting point of 4-nitrophenol, and also the melting point of acetanilide. If 50 g of each compound were mixed and placed into a beaker, then a melting point taken by placing a thermometer in the beaker, what would you expect an approximate melting range to be? Why? 3 samples named A, B, and C possess identical melting points, 99-100 degree C. When a 3:1 mixture of B and C is prepared, its melting point is 50-80 degree C. The melting point of a 2:1 mixture A and C is 99-100 degree C. All melting points of the mixtures were taken in large scale in a beaker. What would you expect as an approximate melting range for a 3:1 mixture of A and B? Explain your reasoning, using what you know about mp's A sample taken on a melting point apparatus was found to melt at 134.2-135.0 degree C. The compound is either cinnamic acid, or urea. Assuming availability of pure urea and cinnamic acid, as well as the sample, how would you determine if the sample was cinnamic acid or urea? (Use only the concepts introduced in this experiment) When performing a melting point on a solid compound. 2 melting point determinations were made. One sample, which was 1 mm in height in the capillary, possessed a melting point of 100-101 degree C. The other sample was 15 mm in height. What would you expect the approximate melting point to be for this 15 mm sample, if the heating rate for both samples was 2 degrees per minute? For the same solid compound as the question above, if the 1 mm sample was heated at 30 degree per minute on a Gallenkamp melting point apparatus, what would you expect for an approximate melting point?

Explanation / Answer

1) Melting point of 4-Nitrophenol is 113 to 114 °C

and so, is the Melting point of acetanilide is 114.3 °C

Since the melting point of the two compounds are same, when these two are mixed together, the melting point of the mixture would be lower than 114 °C. this we can understand with the concept like one of them would act as an impurity for the other.

2) A+ B+C =99-100°Cm

B:C = 3:1 = 50-80°C (B as the major compound and C would act as the impurity, therefore theremust be the dpression in the melting point of B)

A:C = 2:1 = 99-100°C (A as the major compound and C would act as the impurity, therefore theremust be the dpression in the melting point of A)

A:B = 3:1

now, here A is the major compound ad B would act as the impurity. the melting point depression from A would be seen. The range can be between 90-100°C

Question 3) Melting point of Cinnamic acid is 133 °C

Melting point of Urea is 133 °C

Now, the unknown sample is taken and mixed with the sample of urea and cinnamic acid one by one. If the new mp remains same with any one of them, that is the compound because with the other one, it would show changes in its melting point. It would probably decrease as probably the pure sample that we added to the sample would act as an impurity if it is not the same compound.

now, the sample is expected to be urea.

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