Student in O-Chem Lab conducts a melting point experiment with an unknown compound and observes a melting range of 210 – 218C. Is this a typical range for a melting point? If not, what range would be typical?
For this question, does it mean an unknown compound in general? I am thinking that this melting point is sort of typical depending on what the unknown compound is. I don't know if that reasoning is correct tho.
No, the reasoning is not correct. PURE compounds have a melting point range of a few tenths of a degree to perhaps as much as 2 degrees. Generally, the purer the compound the smaller the range. A range of 8 degrees is not typical of a pure organic compound and tells you immediately that the unknown is not a pure substance. Here is a site that talks about the range a little. Note the remark that the melting point can NOT be higher than the literature value since impurities LOWER the melting point.
http://www.csi.edu/ip/physci/faculty/rex/MPTips.htm
You're on the right track! The melting point range of a compound can provide valuable information about its identity and purity. The typical melting point range of a compound will depend on its chemical structure and properties.
In general, pure organic compounds tend to have a relatively narrow melting point range, typically within a few degrees Celsius. This is because the melting process involves breaking intermolecular forces and transitioning from a solid to a liquid state.
However, for mixtures or impure compounds, the melting point range can be broader and have a lower or higher melting point than the pure compound. Impurities or mixtures can disrupt the organization of the molecules, resulting in a broader or lower/higher melting point range.
In your case, the observed melting point range of 210 - 218°C for the unknown compound is relatively broad. This could suggest that the compound is impure, containing various components with different melting points. However, we cannot definitively determine the significance of this range without knowing the specific compound and its expected melting point.
To confirm the identity and purity of the unknown compound, it would be necessary to compare its melting point range with known data for various compounds. This can be done by referencing databases or consulting literature sources that provide melting point information for specific compounds. Analyzing the melting point range in conjunction with other analytical techniques can help in identifying the compound.