Table of Contents
How do you determine the melting point of a compound?
The melting point of an organic solid can be determined by introducing a tiny amount into a small capillary tube, attaching this to the stem of a thermometer centred in a heating bath, heating the bath slowly, and observing the temperatures at which melting begins and is complete.
How can you determine if a compound is decomposing or melting?
If you observe decomposition, record the melting range as the temperature range followed by a lower case “d” to indicate “decomposition.” This is the same convention used by those who compile tables of physical data: a “dec” or “d” after the melting point of a compound denotes decomposition.
Does decomposition affect melting point?
WHEN an organic substance commences to decompose before it melts, the melting point is lowered by the products of decomposition, and depends on the time the sample has been subjected to the decomposition temperature.
How by determining the melting point we can detect an unknown compound?
If two substances melt at the same temperature, a Mixed Melting Point determination can reveal if they are one and the same substance. The phenomenon of melting point depression can be applied to the identification of unknown pure substances.
How to determine the melting point of a compound?
Make note of the temperature (t2) as soon as the compound is melted completely. The average of the two readings gives the correct melting point of the substance. Take Benzoic acid on a tile and crush it into a fine powder.
Why are melting points used in this experiment?
Organic compounds are used in this experiment for the same reasons. Melting points are also used as an indication of purity. Substances melt throughout a temperature range in which both the solid and liquid phases of the substance coexist in a state of equilibrium.
What happens when a compound melts over a wide range?
If the compound melts over a very narrow range, it can usually be assumed that the compound is relatively pure. Conversely, compounds that melt over a wide range are assumed to be relatively impure. Besides melting over a wide range, impure solids also melt at a temperature lower than that for the pure compound.
Which is the end of the melting point range?
The temperature at which all solid has melted is recorded as the end of the melting point range. Upon heating, the solid may expand and move slightly in the tube. This movement should not be interpreted as the beginning of the MP range.