5.1 - Empirical and Molecular Formula

Question 1

What is Empirical formula?

Answer 1

The Empirical formula shows the smallest whole number ratio of atoms of each element in a compound.

Question 2

How can the Empirical formula be calculated?

Answer 2

1) Mass or % composition of mass/ Relative atomic mass (Mr)
2) Divide by smallest number of the answers
3) This should give a whole number ratio like 1:2
4) These whole number are used to write the Empirical formula.

Question 3

Give an example of calculating using masses?

Answer 3

Mass of copper oxide = 4.29g
Mass of coper = 3.43
Mass of oxygen removed = 4.28 - 3.43 = 0.85g

Copper Oxygen
3.43/63.5 0.85/16
0.0540 0.0531
0.0531 0.0531
1 1

CUO ratio is 1:1