Reacting masses calculations - Higher tier

If you have a balanced equation for a reaction, you can calculate the masses of reactants and products.

Sample question

Look at this equation: CaCO₃(s)    →    CaO(s) + CO₂(g)

If we have 50g of CaCO₃, how much CaO can we make?

First, work out the M_r values for the two compounds:

M_r of CaCO₃ is 40 + 12 + 16 + 16 + 16 = 100

M_r of CaO is 40 + 16 = 56

This means that 100 g of CaCO₃ would yield 56 g of CaO in this reaction. In the question we are told we have only half of that amount of CaCO₃, 50 g. So we will get half the amount of CaO, 28 g.

So the mass of CaO we can make = 28 g

Notice in this that 22 g of CO₂ would also be produced, as 50 - 28 = 22