Quantitative Chemistry

Quantitative Chemistry is the calculation unit, covering conservation of mass, relative formula mass, moles, reacting mass calculations, limiting reactants, concentration, and at Higher tier percentage yield, atom economy and gas volumes.

Moles are the concept everything else depends on, so secure the relationship between mass, relative formula mass and number of moles before attempting anything further. Reacting mass questions follow a fixed method: work out moles of the known substance, use the balanced equation ratio, then convert back to mass. Students lose most marks by skipping the ratio step, by using relative atomic mass where relative formula mass is needed, and by not converting units — grams and kilograms, cubic centimetres and cubic decimetres. Show every stage, because method marks are available throughout even when the final figure is wrong.