Question

A known compound has a melting point range of 134-137 degrees. You record a melting point range of 125-126 degrees Celsius for a sample. Is this sample a pure compound?

Answer 1

The sample is not pure. It has small impurities in it.

Step-by-step explanation:

When the substance are pure, they have

• Sharp M.P
• Short range of M.P
• Higher M.P as compare to impure.

In the above case, the known sample has M.P 134-137 centigrade, while recorded sample has M.P 125-126 degrees Celsius that's shows lowering of M.P is due to small amount of impurities.

Reason:

I.M.F become weak when impurities are present which consequently causes the lowering of M.P

Answer 2

The sample for which melting point is being measured is not a pure sample.

It is observed that if a compound shows a lower temperature than the predicted melting point temperature / melting point range it is due to presence of impurity in the sample.

The presence of impurities decreases the melting point of any substance.