Chemists use relative atomic masses and relative formula masses to carry out mole calculations.
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.
What mass of nitrogen is needed to make 120 g of nitrogen monoxide?
(Mr of NO = 30) (Mr 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 Mr
= 2 × 28
= 56 g