The percent recovery in recrystallization is usually less than 100% (although so

Question

The percent recovery in recrystallization is usually less than 100% (although sometimes it can be 100% or larger, see the next problem). This is due to loss of impurity, some material left dissolved in the mother liquor and "mechanical losses". Explain what these mechanical losses really are. When you calculate a percent recovery you may find sometimes that it is larger than 100%. Assuming this is NOT due to errors associated with zeroing the balance, subtracting the weight of the watch glass or weigh paper, or inaccuracies in the balance calibration, suggest a possible reason for this. Intermolecular forces are not chemical bonds. Below are two acetonitrile molecules, add to the drawing the delta + and delta symbols to indicate the atoms with the largest partial charges, AND draw the dipole-dipole intermolecular forces using the dashed-line notation for intermolecular forces that we use in these lab packets. Clearly indicate the dipole-dipole interactions that you drew.

Explanation / Answer

5.

These losses are:

The primary source of mass loss is the solvent i.e., when the sample contains insoluble material, such as insoluble salts, debris etc., these are separated from the hot solution. Actually, it is the impurities that is lost. Hence, removing the impure material causes the percent recovery in recrystallization less than 100%.

Further, additional mass will be lost due to physical handling.

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