IB Chemistry HL 2.1.4 Percentage Yield Questions

Use real HL exam questions to calculate theoretical and percentage yield and explain why experimental recovery is below 100%.

Exam points

Calculate theoretical product amount from the balanced equation and supplied reactant mass, amount or volume.
Calculate percentage yield as actual experimental yield divided by theoretical yield multiplied by 100%, with consistent units.
Interpret a yield below 100% using product loss, incomplete reaction or recovery limitations supported by the question context.

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Study 2.1.4—Percentage yield conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 2]

Phenylethene (styrene) is produced from ethylbenzene in a gas-phase equilibrium.

Figure for Question IB Chemistry HL 2.1.4 Percentage Yield Questions question 1 — IB Chemistry HL

Calculate the mass, in g , of styrene produced from 1.0 kg of ethylbenzene if the yield of the reaction is 90 %.

$\begin{aligned} \text { «mol styrene }=\frac{90}{100} \times \frac{1000}{8(12.01)+10(1.01)} \text { » } \text { «mol styrene }=\text { » } 8.48 \text { «mol» } \text { «mass styrene }=8.48 \times(8(12.01)+8(1.01))=882.88 \text { » } \text { «mass styrene }=\text { » } 880 \text { «g» } \end{aligned}$

Award [2] for correct final answer in range 880-890 «g».

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IB Chemistry HL 2.1.4 Percentage Yield Questions question 1