AQA · Chemistry · 8462
GCSE Chemistry (AQA): Atom Economy
Topic 3 — Quantitative Chemistry. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - Atom Economy - Calculations | Why it's Important (2027/28 exams)"; each card deep-links to the moment in the video it came from. Lesson 3.09 of Cognito's AQA GCSE Chemistry (Triple) course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-t_3.09.
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In the reaction CO + H₂O → H₂ + CO₂, what is the total Mr of the reactants?
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46 (CO = 28 and H₂O = 18).
Why is a low atom economy considered unsustainable?
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It uses up large quantities of raw materials to make only a tiny amount of useful product.
Selling waste as a useful ? is better than paying for its disposal.
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by-product
What is atom economy?
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The percentage of the mass of the reactants that ends up as the desired product.
What atom economy does a reaction have if the desired product is the only product?
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100%, because no reactant mass is converted into waste products.
What is the atom economy of CO + H₂O → H₂ + CO₂ when hydrogen is the desired product?
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4.35% — Mr(H₂) = 2, total Mr of reactants = 46, so (2 ÷ 46) × 100 = 4.35%.
Why does a low atom economy make an industrial process less profitable?
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Raw materials are expensive, and most of them are converted into waste rather than the useful product.
What is the equation for atom economy?
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Atom economy = (Mr of desired product ÷ total Mr of all reactants) × 100.
Give one environmental reason why a low atom economy is a problem.
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Waste products can damage the environment (and are expensive to dispose of).
Name two ways a company can reduce the problems caused by a low atom economy.
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Use a more efficient reaction, or find a use for the waste so it becomes a useful by-product.
Besides atom economy, name three factors affecting how profitable a reaction is.
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Percentage yield, cost of raw materials, and the rate of reaction (also equilibrium position and the cost of maintaining conditions).
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