AS Chemistry question help empirical formula

Mass of lead = 20.7 g
Mass of oxygen = 22.3 - 20.7 = ...

So now you have mass of lead and mass of oxygen.

Find the moles of each and the mole ratio and hence empirical formula

Is it an oxide? So would you do 1.6/32 rather than 1.6/16 ?

1.6/16. You divide by A_r of the element. We are trying to find the mole ratio of lead atoms to oxygen atoms in the compound, hence we use A_r in this calculation

Just wanted to add: Lead oxide is a compound of lead and oxygen only. Lead and oxygen are the only 2 elements in it. That is why we could do the calculation in post 2 to find the mass of oxygen in the lead oxide compound.

So is the answer just PbO ?

Yes

Btw if you did divide by 32, you would be finding the ratio Pb:O2 which you would get as 2:1, i.e, Pb2O2. You'd have to simplify it to PbO