This question is about the extraction of metals - AQA - GCSE Chemistry - Question 3 - 2021 - Paper 1

Based on the calculated relative atomic mass of R, which is 96, element R is molybdenum (Mo) as per the periodic table.

The total molar mass of the reactants in the reaction $SnO_2 + C ⟶ Sn + CO_2$ is:

• $SnO_2$: 119 (Sn) + 32 (O) = 151 g/mol
• $C$: 12 g/mol

Total = 151 + 12 = 163 g/mol.

The product of interest (Sn) has a molar mass of 119. Therefore, the percentage atom economy is given by:

$ext{Atom Economy} = \left( \frac{\text{mass of desired product}}{\text{total mass of reactants}} \right) \times 100 = \left( \frac{119}{163} \right) \times 100 \approx 73\%$.

Hence, the percentage atom economy for extracting tin is approximately 73%.

When evaluating the three methods for extracting tungsten:

1. Carbon: Carbon is the cheapest reactant, but it produces carbon dioxide, which may have environmental impacts. Furthermore, the separation of tungsten from tungsten carbide can be complex and may result in the loss of some tungsten.

2. Hydrogen: Hydrogen requires high purity and generates water vapor as a byproduct, which can easily escape, leading to wastage but is a cleaner option overall.

3. Iron: Iron is the most expensive reactant, and the separation process can be labor-intensive, which raises costs significantly.

In summary, while carbon is economically favorable, it poses environmental risks, whereas hydrogen, despite its challenges, offers a more sustainable approach with less waste.