Moles Equations

Question 1

How do you calculate relative formula mass?

Answer 1

Add together the mass numbers

Question 2

Hwo do you work out moles?

Answer 2

Moles = Mass/Mr

Question 3

How do you work out percentage composition?

Answer 3

Composition = 100 x (no. of atoms x mass of atoms) / (relative formula mass of compound)

Question 4

How do you calculate empirical formula?

Answer 4

Use the table to work out:
1) mass for both
2) Ar for both
3) moles for both
4) then the ratio

Question 5

How do you work out waters of crystallisation?

Answer 5

Find x:
1) work out mass of both
2) work out Mr of both
3) work out moles of both
4) use ratio to find x

Question 6

How do you work out reacting mass ratios?

Answer 6

Use the ticks and question mark method:
1) work out ratio between tick and question mark
2) work out mole of tick
3) use both to work out mole of question mark
4) use mole and Mr of question mark to get mass

Question 8

How do you work out limits and excess questions?

Answer 8

Work out mol of each compound and which ever is larger is in excess / whichever is smaller is limiting.

Question 9

How do you work out percentage yield?

Answer 9

100 x actual yield / theoretical yield