Melting point determination

Question 1

what is mpt determination used for

Answer 1

estimate purity of organic solid, doesn’t purify it/separate it out

Question 2

why does organic solid need to be crushed?

Answer 2

small particle size for analysis, so can get it into tube

Question 3

method

Answer 3

1. powder sample of solid by crushing gently onto surface of filter paper or with mortar and pestle
2. fill 3 melting point tubes with organic solid until depth of 0.5cm
3. set up melting point apparatus and mount one of melting point tubes
4. heat apparatus gently and observe temp at which solid collapses into liquid
5. allow melting point apparatus to cool and repeat measurement of melting point of solid with the 2 other samples. if first reading was approx value, subsequent 2 samples can be done much more slowly as approx value is reached

Question 4

what is good thing about mpt determination

Answer 4

only uses tiny amount of organic product

Question 5

talk me through the main parts of apparatus

Answer 5

magnifying viewing window, hole for tube, thermometer, heat controller

Question 6

how should it be heated and wy?

Answer 6

slowly
if too fast, sample may have melted and thermometer has not reached that temperature reading yet, not kept up so then melting point will appear lower than it acc is

Question 7

melting point of pure substance

Answer 7

sharp

close to data book value

Question 8

melting point of impure substance

Answer 8

wide range

not close to data book value