Reacting Masses Flashcards

All 3 cards in this deck

In a balanced equation, what links the number of moles of a reactant and a product?

The ratio of the numbers in front of their formulae.

e.g. in $2\mathrm{Mg} + \mathrm{O_2} \rightarrow 2\mathrm{MgO}$, 2 mol Mg gives 2 mol MgO (a 1 : 1 ratio).

In a reacting mass calculation using a mass ratio, what units does the answer come out in?

The units of the mass given in the question, e.g. tonnes in gives tonnes out.

What does the mass ratio $160 : 112$ from $\mathrm{Fe_2O_3}$ to $2\mathrm{Fe}$ tell you?

160 tonnes of $\mathrm{Fe_2O_3}$ gives 112 tonnes of iron, so iron is $112/160 = 0.7$ of the oxide's mass.