Quantitative chemistry - (CCEA) Calculate masses from equations (Higher)

Balanced equations and relative formula mass can be used to calculate the mass of product made from a given mass of reactant, and vice versa.

Example:

What mass of nitrogen is needed to make 120 g of nitrogen monoxide? (M_r of NO = 30) (M_r of N₂ = 28)

N₂(g) + O₂(g) → 2NO(g)

= 4 mol

1 mol N₂ : 2 mol NO.

∴

2 mol of N₂ makes 4 mol of NO.

Mass of 2 mol of N₂ = moles x M_r

= 2 × 28

= 56 g