1) The following diagram shows the energy profi le for a reaction.

A catalyst reduces the activation energy by 250 kJ mol^–1. The value of the enthalpy change, in kJ mol^–1, of the catalysed reaction is
A. –600
B. 400
C. 750
D. 1000

Solution

2) The diagram below represents the distribution of kinetic energy in a sample of gaseous reactant molecules. Activation energy E_a1 can be changed to activation energy E_a2.

This change increases the reaction rate. Which of the following gives the most likely cause of the change from E_a1 to E_a2 and explains why the reaction rate would increase?

Solution

3) The equation for cellular respiration is as follows.

When 72.0 g of glucose, C₆H₁₂O₆, is metabolised in cellular respiration, the total energy released is 1.126 × 10³ kJ. The value of ΔH, in kJ mol^–1, for the equation above is
A. –1.56 × 10¹
B. –4.50 × 10²
C. –2.82 × 10³
D. –8.11 × 10⁴

Solution