SCH3U Quantities in Chemical Reactions

Question

Solutions of iron(III) chloride, FeCl₃, are used in photoengraving and to make ink. This compound can be made by the following reaction.

2Fe + 3Cl₂ = 2FeCl₃



a)     How many moles of FeCl₃ form from 31 mol of Cl₂?

b)    How many moles of Fe are needed to combine with 5 mol of Cl₂ by this reaction?

c)     If 0.62 mol of Fe is to be used by this reaction, how many moles of FeCl₃ form?

Answer 1

2Fe + 3Cl₂ = 2FeCl₃ ... balanced equation

Using the mol ratios in the balanced equation, we can answer the question as follows:

a) 31 mol Cl₂ x 2 mol FeCl₃ / 3 mol Cl₂ = 21 mols FeCl₃ (2 sig. figs.)

b) 5 mol Cl₂ x 2 mol Fe / 3 mol Cl₂ =3 mol Fe (1 sig. fig.)

c) 0.62 mol Fe x 2 mol FeCl₃ / 2 mol Fe = 0.62 mol FeCl₃ (2 sig. figs.)