page 02 SECTION 1 — 20 marks Attempt ALL questions 1. The potential energy diagram below refers to the reversible reaction involving reactants R and products P. P R 90 80 70 60 50 40 30 20 10 0 Potential energy (kJ mol−1) Reaction pathway What is the enthalpy change, in kJ mol−1, for the reverse reaction? A −40 B −10 C +10 D +30 2. The relative rate of a reaction which reached completion in 1 minute 40 seconds is A 0·010 s−1 B 0·714 s−1 C 0·010 min−1 D 0·714 min−1. page 03 3. T1 Kinetic energy of molecules T2 Number of molecules EA Which of the following is the correct interpretation of the above energy distribution diagram for a reaction as the temperature decreases from T2 to T1? Activation energy (EA) Number of successful collisions A remains the same increases B decreases decreases C decreases increases D remains the same decreases 4. The table shows the first three ionisation energies of aluminium. Ionisation energy (kJ mol−1) First Second Third 578 1817 2745 Using this information, what is the enthalpy change, in kJ mol−1, for the following reaction? Al+(g) ↓ Al3+(g) + 2e− A 1817 B 2395 C 4562 D 5140 [Turn over