Question

what mass of carbon dioxide will be produced when 29.9 g of butane reacts with an excess of oxygen in 2C4H10(g) + 13O2(g) = 8CO2(g) + 10H2O(g)

Answer 1

Calculate first amount of butane n = m/M.

Then you see from reaction equation two moles butane
yields 8 moles CO2 and one mole 4 moles CO2

You can calculate number of moles of CO2 and
mass is m = n * M