Chemistry question

Question

Copper can be recovered from scrap metal by adding sulfuric acid. Soluble copper sulfate is formed. The copper sulfate then reacts with metallic iron in a single displacement reaction. A student places 1.942 g of iron wool in a beak that contains 136.3 mL of 0.0750 M aqueous copper (II) sulfate. What mass of copper is formed?

Im just lost, what kind of things should i be thinking of when doing this? Is there a special way to solve problems like these? Please help.

Answer 1

Hi Gongo! Every stoichiometry problem is different, but I'll break down the steps I think work well and use your question as an example.

1) Write a balanced equation for the reaction occurring. (*Iron occurs in a few different oxidation states, but I will assume we're referring to Fe(II) or Fe²⁺)

Fe + CuSO₄ -> Cu + FeSO₄

2) Calculate the number of moles of each reactant.

Fe: 1.924 g * (1 mol / 55.85 g) = 0.03455 mol Fe

CuSO₄: 0.1363 L * (0.0750 mol / 1 L) = 0.01022 mol CuSO₄

3) Determine the limiting reactant. Because we have fewer moles of copper(II) sulfate and are reacting both reactants in a 1:1 ratio, we will run out of copper(II) sulfate first, making it the limiting reactant.

4) Convert moles of the limiting reactant to moles and grams of product of interest.

0.01022 CuSO₄ (1 mol Cu / 1 mol CuSO₄ ) (63.55 g Cu / 1 mol Cu) = 0.6495 g Cu

A few tips to remember as you give your final answer...

1. Check for significant digits
2. Ensure you write the number with an appropriate unit and chemical species
3. Ensure your answer makes common sense
4. Balance your equations