Year 12 Chemistry Chapter 2

A sample of olive oil with a wick in a jar is ignited and used to heat a beaker containing 500.0 g of water, H₂O. The relevant data for the experiment is included in the table to the left.

After complete combustion of 2.97 g of olive oil, the final temperature of the water, in degrees Celsius, would be

• 44.9

• 58.0

• 65.9

• 79.3

The energy profile diagram to the left represents a particular reaction. One graph represents the uncatalysed reaction and the other graph represents the catalysed reaction. Which of the following best matches the energy profile diagram?

• 
• 
• 
• 

An equation for the complete combustion of methanol is

2CH₃OH(l) + 3O₂(g) → 2CO₂(g) + 4H₂O(g)

ΔH for this equation would be

• +726 kJ mol^–1

• -726 kJ mol^–1

• +1452 kJ mol^–1

• -1452 kJ mol^–1

Four fuels undergo complete combustion in excess oxygen, O₂, and the energy released is used to heat 1000 g of water.

Assuming there is no energy lost to the environment, which one of these fuels will increase the temperature of the water from 25.0 °C to 85.0 °C?

• 0.889 g of hydrogen, H₂

• 3.95 g of propane, C₃H₈

• 0.282 mol of methane, CH₄

• 0.301 mol of methanol, CH₃OH

The molar heat of combustion of pentan-1-ol, C₅H₁₁OH, is 3329 kJ mol^–1.

M(C₅H₁₁OH) = 88.0 g mol^–1

The mass of C₅H₁₁OH, in tonnes, required to produce 10 800 MJ of energy is closest to

• 0.0286

• 0.286

• 2.86

• 286

Using the same scale, the energy profiles of four different reactions are shown to the left.

Which diagram shows the most likely energy profile for a fuel?

• 1

• 2

• 3

• 4

In which of the diagrams shown to the left is the activation energy for the forward reaction greater than the magnitude of the enthalpy change for the reverse reaction?

• 1 only

• 1 and 3 only

• 2 and 4 only

• 4 only

Which one of the following statements is true for endothermic reactions but not for exothermic reactions?

• The activation energy of the reaction is always a positive value.

• There is a change in enthalpy that occurs during the reaction.

• The energy content of the products is higher than the reactants.

• The temperature of the surroundings is higher after the reaction.

When 0.173 mol of a particular fuel is burnt completely, 225 kJ of energy is produced.

The fuel is likely to be

• ethane

• ethyne

• ethanol

• propane

What is the total energy released, in kilojoules, when 100 g of butane and 200 g of octane undergo combustion in the presence of excess oxygen?

• 9760

• 14 600

• 17 300

• 19 500