Heating in Crucible

Question 1

Why do we use this method?

Answer 1

• Used for measuring mass loss in various thermal decomposition reactions.
• mass gain when reacting magnesium in oxygen

Question 2

Describe the method of heating in a crucible

Answer 2

1) weigh empty clean dry crucible and lid
2) add 2g of hydrated calcium sulfate to the crucible and weigh again
3) Heat strongly with bunsen burner for a couple of minutes
4) allow to cool
5) weigh the crucible and contents again
6) heat crucible again and reweigh until you reach a constant mass (this makes sure reaction in complete)

Question 3

why shouldnt large amounts of hydrated calcium sulfate be used in this experiment?

Answer 3

decomposition is likely to be incomplete

Question 4

why should the crucible be dry

Answer 4

wet crucible would give inaccurate result

- mass loss would be too large as water would be lost when heating.

Question 5

why should small amounts of solid be used (0.1g) in this experiment?

Answer 5

percentage uncertainties would be too high

Question 6

how can you improve the accuracy of this experiment?

Answer 6

-use a lid
prevents loss of solid
should be loose fitting to allow the gas to escape