topic 1 calcualtions

Question 1

What is the empirical formula

Answer 1

simplist ratio of atoms
e.g. C6 H12 O6 = C H2 O

Question 2

what is avergadro’s constant

Answer 2

6.03 *10 to the power of 23

Question 3

How to work out number of moles

Answer 3

Number of moles = Mass in g / relative formula mass

Question 4

How to calculate concentration

Answer 4

concentration (g dm-3) = mass of solute (g) / volume of solution (dm3)

Question 5

How can you use experiments to find empirical formula

Answer 5

1) heat a crucible till red hot ( to clean it)
2) Let it cool then weigh it
3) Add clean magnesium ribbon. Reweigh to measure mass of ribbon.
4) Heat crucible and keep lid on to stop any solids escaping but leave small gap for oxygen
5) Heat till ribbon turned white
6) Let magnesium cool and reweigh. To measure mass of magnesium oxide

Question 6

What are limiting reactants

Answer 6

When all of one reactant is used up and limits the reaction

Question 7

How to calculate amount of product from the limiting reactant.

Answer 7

1) write balanced equation
2) work out relative formula mass of reactants and product
3) work out moles of substance you know the mass of
4) Work out how many moles will be of the other substance
5) use number of moles to calculate mass