PAG 2.3 hydrated salt

Question 1

experiment 1 for finding the formula of hydrated copper II sulfate

Answer 1

1) weigh an empty crucible
2) add 2g of hydrated copper II sulfate to the crucible and reweigh
3) place crucible on pipe-clay triangle and heat gently for 1 min then strongly for 5 min
4) leave to cool for at least 5 mins and reweigh the crucible
5) heat the crucible again then leave to cool and reweigh
6) repeat step 6 until mass remains constant
8) stop heating if a red colouration appears in the white powder

Question 2

experiment 2 for finding the formula of hydrated barium chloride

Answer 2

1) weigh an empty crucible
2) add 2g of hydrated barium chloride to the crucible and reweigh
3) place the crucible on the pipe-clay triangle and heat gently for 1 min then strongly for 5 min
4) leave to cool for 5 mins and reweigh the crucible
5) heat the crucible again then leave to cool and reweigh
7) heat till constant mass

Question 3

why is it important to keep heating the salt until the mass remains constant?

Answer 3

to ensure that all the water has been removed by evaporation