Measuring the Melting Points of Compounds and Mixtures

Question 1

objective

Answer 1

• finding melting point of pure benzoic acid and acetanilide
• compare melting point in data table

Question 2

loading a melting capillary tube

Answer 2

1. crush compound
2. tap capillary tube in the crude powder
3. use tapper on digimelt
4. mount capillary tube into the digimelt

Question 3

melting point

Answer 3

solid state is in equilibrium with the liquid state

Question 4

melting point range q

Answer 4

temperature range over which crystals first begin to liquefy up until the point at which the entire sample is in liquid form

Question 5

What does the melting range show? pure or impure?

Answer 5

narrow range- pure

broad range- impure

Question 6

sweating

Answer 6

shouldn’t be mistaken for melting

Question 7

at the melting point of a compound what is occurring to the intermolcular forces that hold the molecules together and keep it in its solid state?

Answer 7

the melting point is has acquired energy to break the intermolecular forces changing it to liquid form

Question 8

WHat are the two ways that melting point can be used to assess the purity of a mixture?

Answer 8

1. the purer the material, the higher the melting point

2. the purer the material, the narrower the melting point range

Question 9

How does the addition of successive amounts of an impurity affect the melting point?

Answer 9

melting point will decrease in proportion to the amount of impurity