Melting and Boiling Points

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Data and calculations:

The data sheet was attached.

Calculated the melting point range for each solid:

-The melting point range of p-dichlorobenzene: 58.1-53.5=4.6

-The melting point range of acetamide: 84.5-79.2=5.3

-The melting point range of solid mixture: 83.5-58.1=25.4

Sources of errors:

-Because of the heating process, the mixture of liquid may vaporize before the temperature reaches at the boiling point.

-When the solid samples were grinded on the lab table, the pure solid may be contaminated from the environment or the dirt on the table.

-When determine the “half-melted”, it is hard to decide the subject half-melted. So melting point may be inaccurate.

Conclusion:

Part A. Melting Point Determine

-According to the data sheet, the experimental melting point of p-dichlorobenzene was 56.5°C, while the accepted melting point is 52.7°C. And the melting point range of p-dichlorobenzene was 4.6. Applied the definition of the melting point of impure solid, it says that impure solid usually has a wide melting point change (>4°C), and its melting point usually lower than the accepted point. The acetamide got the same result; the experimental melting point (82.3°C) was higher than the accepted melting point (79°C). For these two experiments results, they didn’t comply with the definition; it maybe because the given pure samples were contaminated from the dirt on the table.

-For the result of solid mixture melting point, the experimental melting point was 74.9, and the range was 25.4. Applied the definition, it was impure. The melting point of the mixture was higher than the p-dichlorobenzene, while lower than the acetamide. This may because when mixed two solids together, more acetamide was put into the mixture.

Part B. Boiling Point Determine

-By doing research, known that the accepted boiling point of acetone is 56°C, while the experimental boiling point was 56.4°C, so the given liquid is a pure liquid. For the mixture of acetone and ethyl alcohol liquid, the experimental boiling point was 67.6°C, this result was higher than the accepted value of acetone, so we can regard this mixture liquid as a impure liquid.

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