AQA · Chemistry · 8462
GCSE Chemistry (AQA): Percentage Yield
Topic 3 — Quantitative Chemistry. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - Percentage Yield - Theoretical & Actual Yield | Calculations (2027/28 exams)"; each card deep-links to the moment in the video it came from. Lesson 3.1 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_3.1.
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In the Haber process, which side reaction with air can reduce the ammonia yield?
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Nitrogen reacting with oxygen from the air to form nitrogen dioxide instead of ammonia.
What is the theoretical yield of a reaction?
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The mass (or moles) of product you would expect to get based on calculations, assuming the reaction goes perfectly.
Why can a reversible reaction never give a 100% yield?
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It reaches equilibrium, so some product keeps breaking back down into the reactants and the reaction never goes to completion.
What is the maximum possible percentage yield of a reaction?
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100%, obtained only if all the predicted product is collected.
Calculate the percentage yield if the actual yield is 15 g and the theoretical yield is 18 g.
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83.3% (15 ÷ 18 × 100).
What is the actual yield of a reaction?
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The mass (or moles) of product actually obtained when the reaction is carried out.
Give one way product is physically lost during a reaction or separation.
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Gaseous products escape into the air, or solid/liquid is left behind on the filter paper or in the test tube.
Why is it hard to recover all the liquid when filtering a mixture?
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Some liquid stays in the test tube, some remains on the solid, and some soaks into the filter paper.
Reacting 2 g of hydrogen with 16 g of oxygen gives what theoretical yield of water?
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18 g, because mass is conserved: 2 g + 16 g = 18 g.
A reaction that has not had enough time to finish will leave some of the mixture as unreacted ?.
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reactants
What is the equation for percentage yield?
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Percentage yield = (actual yield ÷ theoretical yield) × 100
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