Question

When performing a melting point on a solid compound, 2 melting point determinations were made. One sample, which was 1 mm in height in the capillary, possessed a melting point of 150-151°C. The other sample was 25 mm in height. What would you expect the approximate melting point to be for this 25 mm sample, if the heating rate for both samples was 2 degrees per minute? (Hint: use algebra to solve the mp range) 4.

Answer 1

The temperature increases all time, the solid samples will take some time to melt, you might be expected variation in answers. However, you should consider the melting point of solid is when the sample FIRST shows the sign of melting [ but not when all melt] so you should get the same melting point every time when temperature rise is relatively slow.

In the second sample, the solid sample warms too fast, so when the melting starts, the temperature has been already risen and read that temperature by the thermometer at the same time. As the temperature rising 0.2°C per second, it depends how long it takes to get a reading. 5sec? then it'll be 1 degree out, 10 sec will give 2 degrees out of true