Melting Points and Mixed Melting Points 1)A solid sample has a MP of 133 - 139°C
ID: 1652897 • Letter: M
Question
Melting Points and Mixed Melting Points
1)A solid sample has a MP of 133 - 139°C. What can one conclude about the sample?
2) How can you tell that a compound has decomposed on melting?
3) Two test tubes contain compounds having the same MP. Using MPs, how could you determine whether the two test tubes contain the same or different compounds?
4) In a recrystallization, a solid is dissolved in a solvent and later the solvent is removed. If a MP of the sample is taken while the sample is still moist with solvent, what effect would that have on the MP of the sample?
Explanation / Answer
1 ) In solids, there is no specific melting point but a range of melting points. If the range is too wide, the solid is called as an impure subtance. As there is a difference of 6 degree celsius in given meltin points, the solid under consideration is most probably an impure one. Impure solids melt at a lower temperature than a pure solid.
2) if the compound has decomposed, it will not have same melting point anymore.
3) Find the melting point of each compound. Then mix the two compounds and try to find out if melting point of the mixture has lowered or stayed the same. If it has lowered, the mixed compound will be relatively impure and this means that both the test tubes contain different compounds.
4) The melting point range will be much higher and it will be lower than the actual Melting point of the sample.