1. Consider the following features of a chemical reaction.

I. activation energy
II. ∆H of the reaction
III. enthalpy of the reactants Compared with the uncatalysed reaction pathway, the presence of a catalyst changes
A. I only.
B. II only.
C. II and III only.
D. I, II and III.

Solution

2. Lignite is a type of brown coal. When lignite is completely combusted in a power station, 19.0 MJ/tonne of energy is released. The efficiency of the power station is 39%. What mass of lignite is required to produce 42.0 MJ of usable energy in the power station?
A. 0.862 tonnes
B. 1.16 tonnes
C. 2.21 tonnes
D. 5.67 tonnes

Solution

3. a. Propane is used as a fuel for barbeques.

i. Calculate the amount of energy released when 140.0 g of propane is completely combusted. 1 mark

ii. Write a thermochemical equation for the complete combustion of propane at SLC. 2 marks

Solution

b. Sketch the energy profile for the complete combustion of propane on the axes provided below. 1 mark

Solution

c. State how the energy profile for the incomplete combustion of propane would differ from the diagram you drew in part b. Justify your answer. 2 marks

Solution

4. An equation for the complete combustion of ethanol, C₂H₅OH, is shown below.
C₂H₅OH (l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l)

a. 96.0 g of ethanol completely combusts and the CO₂ produced is collected. Calculate the minimum volume of a tank required to store the captured CO₂ at 15.0 °C and 100.0 kPa. 3 marks

Solution

b. The molar mass of ethanol is 46.0 g mol−1 and the molar mass of propane is 44.0 g mol−1. State whether the flashpoint of ethanol is higher or lower than the flashpoint of propane. Explain the reasons for your choice with reference to the structure of both molecules. 3 marks

Solution