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This question is about the extraction of metals - AQA - GCSE Chemistry - Question 3 - 2021 - Paper 1
Question 3
This question is about the extraction of metals. Element R is extracted from its oxide by reduction with hydrogen. The equation for the reaction is: $$3H_2 + RO_3... show full transcript
Worked Solution & Example Answer:This question is about the extraction of metals - AQA - GCSE Chemistry - Question 3 - 2021 - Paper 1
Step 1
Calculate the relative atomic mass (A_r) of R
Answer
To find the relative atomic mass (A_r) of R, we start with the equation:
- The sum of the relative formula masses of the reactants is given as 150.
- We calculate the mass of 3H₂:
- The mass of H₂ is 2 * 1 = 2, so 3H₂ = 3 * 2 = 6.
- Substituting this into the equation:
- 6 + M_R = 150,
- Thus, M_R = 150 - 6 = 144.
- The higher oxidation state of R, being RO₃, indicates R must balance three O, making O = 16.
- Solving gives:
- A_r = 144 - (3 * 16) = 144 - 48 = 96.
Therefore, the relative atomic mass of R is A_r = 96.
Step 2
Step 3
Calculate the percentage atom economy for extracting tin
Answer
To calculate the percentage atom economy, we use the formula:
- The molar mass of Sn: 119.
- Total mass of reactants:
- SnO₂ = 119 + 2 * 16 = 119 + 32 = 151;
- C = 12.
- Total = 151 + 12 = 163.
- Calculate the atom economy:
- Atom Economy = (119 / 163) * 100 ≈ 72.93%.
Thus, the percentage atom economy for extracting tin is approximately 73%.
Step 4
Evaluate the three possible methods for extracting tungsten
Answer
The three methods for extracting tungsten from tungsten oxide (WO₃) include:
-
Carbon:
- Low cost but produces CO₂, thus contributing to pollution. Carbon is likely the cheapest reactant, making it attractive economically.
-
Hydrogen:
- High efficiency and clean (produces water vapor), but relatively high cost of hydrogen makes it less favorable economically despite high atom economy.
-
Iron:
- Medium cost with a considerable amount of solid waste to separate. Involves more complexity in purification but can be effective.
Overall evaluation shows that carbon may be the cheapest method, but hydrogen could be more sustainable in terms of environmental impact despite higher costs.