Quantitive Chemistry Part 2

Question 1

What is meant by water of crystallisation

Answer 1

A solid which is hydrated contains “water of crystallisation”. This is water which is “chemically combined” in the crytal structure.

Question 2

Why do you only evaporate off half of the water in a crystallisation experiment

Answer 2

This increases the concentration of the solution making it super saturated and promoting the formation of crystals

Question 3

Why do crystals form in a crystallisation experiment when cooled

Answer 3

If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound

Question 4

What is the relative formula mass

Answer 4

The sum of the relative atomic mass of all the atoms present in the formula of a substance

Question 6

How do you calculate moles

Answer 6

Mass divided by rfm

Question 7

How do you calculate mass

Answer 7

Moles multiplied by rfm

Question 8

How do you calculate percentage yield

Answer 8

Actual yield divided by theoretical yield x 100

Question 9

How do you calculate percentage of water crystallisation in a compound

Answer 9

Total rfm of water divided by total rfm of compound x100