Melting Point Determination
This larger surface area-to- illume ratio allows for a sharper more accurate melting point. 4. Approximately 20 crystals should be loaded onto the coveralls to ensure that the sample is heated evenly. 5. The temperature of the stage should be ICC below the expected melting point when you begin to heat 1-ICC per minute. 6. The melting point range would increase because the heat would not be able to properly penetrate the sample evenly. This would make the center of the large uncrushed sample have less exposure to the heat, and it would melt much slower than a small and evenly spread sample. . It is important because if the temperature is increased too rapidly at the elating point, the sample and the aluminum block will not be at the thermal equilibrium with the thermometer. 8. Rapidly heating the sample results In too high of a reading because the sample and aluminum bock are not at equilibrium with the mercury in the thermometer and this will result In a very high reading. 9. A mixed melting point analysis Is preformed to determine the identity of an unknown sample.
The unknown sample Is placed In the heating apparatus and heated using a true (slow) melting point. Once the melting point of the unknown Is determined, the known samples are mixed with the unknown to see which one matches the melting mint of the unknown. If the unknown sample and the known sample melt at the same temperature as the unknown then they are the same compound. If they melt before the melt point of the unknown then It Is an Impure compound exhibiting a depressed melting point.
This way we are able to Identify the Identity of the unknown. 10. A. B and C are the same compounds. B. A Is different from B and C. C. It would be very similar to the melting point of B + A since B and C are the same. Therefore It would be approximately 45. 1 – 53. ICC. Crushing the sample allows for greater surface area-to-volume ratio of the powder, equilibrium with the thermometer. . Rapidly heating the sample results in too high mercury in the thermometer and this will result in a very high reading. . A mixed melting point analysis is preformed to determine the identity of an unknown sample.
