2.1.2.2 Formulae for Crystlas and Salts

Question 1

Definition of Hydrated

Answer 1

it refers to a crystalline compound containing water molecules

Question 2

Definition of Anhydrous

Answer 2

it refers to a substance that contains no water molecules

Question 3

Definition of water of crystallisation

Answer 3

It refers to water molecules that form an essential part of the crystalline structure of a compound

Question 4

What is shown before and after the dot in a Dot Formulae

Answer 4

> The empirical formula of the compound is shown before the dot
the relative number of water molecules of crystallisation is shown after the dot.

Question 5

How do you find out the Formulae of the hydrated slat?

Answer 5

1. Calculate the amount, in mol, of anhydrous
2. Calculate the amount, in mol. of water
3. divide the smaller number by the bigger number

Question 6

How do you carry out the experiment?

Answer 6

1. Weight an empty crucible
2. Add the hydrated salt into the weighted crucible. Weight the crucible and the hydrated salt
3. Heat the crucible gently for a minute and then heat it strongly for a further three minute
4. Leave the cubicle to cool and then weigh the crucible and anhydrous salt

Question 7

How do you find out the anhydrous salt?

Answer 7

( mass of crucible + anhydrous salt) - ( mass of crucible)

Question 8

How do you find out the mass of water?

Answer 8

( mass of crucible + hydrated salt ) - ( mass of crucible + anhydrous salt)

Question 9

What are the two assumptions made during this experiment?

Answer 9

> All of the water has been lost

> There is no further decomposition of the salt