This question is about iron - AQA - GCSE Chemistry Combined Science - Question 8 - 2018 - Paper 1

Unreacted iron can be separated from the mixture using filtration or a magnet.

To calculate the mass of iron produced:

1. Calculate moles of magnesium:

   $$ext{Moles of Mg} = \frac{0.120 \text{ g}}{24 \text{ g/mol}} = 0.005 \text{ moles}$$

2. Use the stoichiometry of the reaction:

   From the equation, 3 moles of Mg produce 2 moles of Fe.

   $$\text{Moles of Fe} = \left(0.005 \text{ moles Mg} \right) \times \frac{2 \text{ moles Fe}}{3 \text{ moles Mg}} = 0.00333 \text{ moles Fe}$$

3. Calculate the mass of iron produced:

   $$\text{Mass of Fe} = 0.00333 \text{ moles} \times 56 \text{ g/mol} = 0.18668 \text{ g} = 186.68 ext{ mg}$$

4. Rounding to the appropriate significant figures, the mass of iron produced is approximately 187 mg.

In the reaction, iron (Fe²⁺) is the species that gets reduced. The half equation for this reduction is:

This indicates that iron ions gain electrons to form solid iron.