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Magnesium sulfate, MgSO₄, is made by a neutralisation reaction - OCR Gateway - GCSE Chemistry - Question 20 - 2022 - Paper 1
Question 20
Magnesium sulfate, MgSO₄, is made by a neutralisation reaction. Method 1 and 2 show two different ways of making magnesium sulfate. Method 1 – Reaction of sulfuric... show full transcript
Worked Solution & Example Answer:Magnesium sulfate, MgSO₄, is made by a neutralisation reaction - OCR Gateway - GCSE Chemistry - Question 20 - 2022 - Paper 1
Step 1
Calculate Atom Economy of Method 1
Answer
To find the atom economy of Method 1 (reaction with magnesium carbonate), we first need to calculate the molar masses of the reactants and products.
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The total molar mass of reactants (H₂SO₄ + MgCO₃):
- M(H₂SO₄) = 2(1.0) + 32.1 + 4(16.0) = 98.1 g/mol
- M(MgCO₃) = 24.3 + 12.0 + 3(16.0) = 84.3 g/mol
- Total = 98.1 + 84.3 = 182.4 g/mol
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The molar mass of the useful product (MgSO₄):
- M(MgSO₄) = 24.3 + 32.1 + 4(16.0) = 120.4 g/mol
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Atom Economy = (Mass of useful product / Total mass of reactants) × 100%
- Atom Economy = (120.4 / 182.4) × 100% ≈ 66.0%
Step 2
Calculate Atom Economy of Method 2
Answer
For Method 2 (reaction with magnesium oxide), the calculations are as follows:
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The total molar mass of reactants (H₂SO₄ + MgO):
- M(MgO) = 24.3 + 16.0 = 40.3 g/mol
- Total = 98.1 + 40.3 = 138.4 g/mol
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The molar mass of the product (MgSO₄) remains the same as before: 120.4 g/mol.
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Atom Economy = (Mass of useful product / Total mass of reactants) × 100%
- Atom Economy = (120.4 / 138.4) × 100% ≈ 87.0%
Step 3
Comparison and Conclusion
Answer
Comparing the atom economies:
- Method 1: Approximately 66.0%
- Method 2: Approximately 87.0%
Since the atom economy of Method 2 is higher than that of Method 1, the company should use Method 2 to make magnesium sulfate. This approach is more sustainable as it utilizes resources more efficiently, producing less waste.