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Edexcel A-Level Chemistry A2 12.6 The Total Entropy Change of Any Reaction Is the Sum of the Entropy Change of the System and the Entropy Change of Questions

Write ΔStotal = ΔSsystem + ΔSsurroundings, convert kJ and J before adding and retain the sign and J K⁻¹ mol⁻¹ units in the final value.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

Exam points

  • Calculate ΔStotal by adding system and surroundings entropy changes with signs and units.
  • Rearrange the total-entropy equation to find a missing system or surroundings value.

Edexcel A-Level Chemistry A2 12.6 The Total Entropy Change of Any Reaction Is the Sum of the Entropy Change of the System and the Entropy Change of Questions question 1

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Ammonia is manufactured in the Haber Process.

N2( g)+3H2( g)⇌2NH3( g)\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NH}_{3}(\mathrm{~g})

In this process, pressures between 100 atm and 300 atm and temperatures between 675 K and 725 K are usually used.

At 700 K, the total entropy change, ΔS_total = -78.7 J K⁻¹ mol⁻¹. Calculate ΔS_system for this reaction at 700 K. Include a sign and units in your answer.

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