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3.2 Energetics

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Question 18

A chemist compares two reactions, P and Q. The energy levels on the reaction profiles for the two reactions are shown in the table.

ReactionReactants (kJ/mol\mathrm{kJ/mol}kJ/mol)Peak (kJ/mol\mathrm{kJ/mol}kJ/mol)Products (kJ/mol\mathrm{kJ/mol}kJ/mol)
P4011570
Q5010590
a.

Calculate the activation energy for reaction P.

[1]
b.

Calculate the overall energy change for reaction P. State what this value shows about the type of reaction.

[2]
c.

The chemist wants to use one of these reactions in an instant cold pack. The same number of moles would react in each case.

Explain which reaction, P or Q, would be better for the cold pack. Use data from the table in your answer.

[2]
Markscheme

3.2 Energetics Questions

  1. GCSE
  2. /Chemistry
  3. /3.2 Energetics

106 exam-style questions on OCR GCSE Chemistry 3.2 Energetics, covering 3.2.1 Exothermic and endothermic reactions and reaction profiles and 3.2.2 Calculating energy change from bond energies. Each one has a worked solution and a mark scheme showing where the marks go.

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