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Edexcel A-Level Chemistry AS 1.9 Percentage Yields and Percentage Atom Economies By Mass in Laboratory and Industrial Processes Questions

Practise calculating percentage yield and atom economy from equations, product masses and laboratory or industrial process data.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
AS

Exam points

  • calculate percentage yield from actual mass and the theoretical mass from stoichiometry
  • find atom economy by comparing desired product mass with total product mass
  • interpret when co-products make an industrial route useful despite multiple products

Edexcel A-Level Chemistry AS 1.9 Percentage Yields and Percentage Atom Economies By Mass in Laboratory and Industrial Processes Questions question 1

[Maximum number: 2]

This question is about magnesium, magnesium oxide and magnesium sulfate.

Hydrated crystals of magnesium sulfate, MgSO4⋅7H2O\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}, can be made by reacting magnesium with sulfuric acid.

In an experiment, magnesium was added to 30.0 cm330.0 \mathrm{~cm}^{3} of 0.500 moldm−30.500 \mathrm{~mol} \mathrm{dm}^{-3} sulfuric acid.
[Mr\left[M_{\mathrm{r}}\right. value: MgSO4⋅7H2O=246.4Ar\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}=246.4 \quad A_{\mathrm{r}} value: Mg=24.3]\left.\mathrm{Mg}=24.3\right]

The magnesium sulfate solution was allowed to crystallise.

The crystals were dried and weighed.
The mass of the hydrated crystals, MgSO4⋅7H2O\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}, was 2.78 g .
Calculate the percentage yield in this experiment.

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