Question

If you reacted 93.7 grams of iron with excess copper sulfate solution, what mass of copper would you expect to make? You may need to balance the equation first. Fe + CuSO4 -> Cu +FeSO4 A. 89.18 grams
B. 106.25 grams
C. 1.67 grams
D. 104.5 grams

Answer 1

1)  Chemical equation

Fe + CuSO4 --> Cu + FeSO4

It is already balanced

2) Molar ratios

1 mol Fe : 1 mol CuSO4 : 1 mol Cu : 1 mol FeSO4

3) atomic masses of Fe and Cu

Fe: 55.8 g/mol

Cu: 63.5 g/mol

4) number of moles of Fe

number of moles = mass in grams / atomic mass = 93.7 g / 55.8 g/mol = 1.679 mol

5) number of moles of Cu:

1 mol Fe / 1 mol Cu => 1.679 mol Fe / 1.679 mole Cu

5) mass of Cu in 1.679 moles Cu

mass = atomic mass * number of atoms = 63.5 g/mol * 1.679 moles = 106.6 g = 107 rounded to 3 significant figures.

=> Answer is the option B (although the question should have 3 significant figures).