The Moles Calculations.

Question 1

What is the moles formula?

Answer 1

moles=mass/relative formula mass

Question 2

What is meant by limiting and excess reactant?

Answer 2

The idea that when reacting one of the reactants have to have an excess amount of the substance so that the limiting reactant fully reacts to the extent that it is able to.
Meaning that there will always be extra substance in the product at the end and the amount left of it relies on the limiting reactant and how well it reacts.