In the determination of a melting point, why is it necessary to: use a powdered
ID: 1024263 • Letter: I
Question
In the determination of a melting point, why is it necessary to: use a powdered rather than a crystalline sample? use a new capillary tube for each determination? not heat the sample too rapidly near the melting point? The melting point of a pure unknown compound was found to be 95.4 degree C. The unknown was thought to be one of three known compounds, samples of which were all available. Describe a procedure for identifying the unknown as one of the three known compounds. Which has a lower freezing point: ice or ice cream? Why?Explanation / Answer
Ans. 1 (a) In the powder form heating is uniform so the found meltimg point is accurate.
(b) It is necessay to use new capillary tube for each measurement since capilary tubes are very thin and its is very difficult to clean. Since present imurties changes the meltimg point of the compound. So we can not get the sharp melting point of desired compound.
(c) Heatng the sample nearly melting point will not give the sharp result. It will varied the region of melting point.
2. Make the derivative of all three compound and determine the melting point. It will provide the idea of original compound.
3. Melting point of ice of ice cream have lower melting point since there is depression in freezing point.