Monitoring chemical reactions

C5.1 Monitoring chemical reactions

Summary This topic tackles the relationship of moles to the concentration of a solution and the volume of a gas. It also tackles the calculation of the mass of a substance in terms of its molarity. The topic then moves on to look at using equations to make predictions about yield by calculations and to calculate atom economy. Underlying knowledge and understanding Learners should be familiar with the mole from Topic C3 and know that it measures the amount of substance. They should be familiar with representing chemical reactions using formulae and using equations.

Common misconceptions The most common problem learners’ encounter with these calculations is their lack of understanding of ratios. Also most learners think that the mole and mass are the same thing. This is reinforced by use of phrases such as ‘1 mole is 12 g of carbon, ‘1 mole is the relative atomic mass in grammes’ or ‘1 mol = 12 g C’ in teaching and in textbooks equating amount of substance to mass, portion of substance, number of particles (Avogadro’s number) or number of moles. All these phrases reinforce the idea that amount of substance is a measure of mass or a number.