Carbon-Based Fuels

Which one of the following statements indicates why ethanol produced from sugar cane is defined as a biofuel and ethanol produced from coal is not?

• Ethanol produced from sugar cane generates less greenhouse gases when used as a fuel than ethanol produced from coal.

• Ethanol produced from coal can be used to generate electrical energy whereas ethanol produced from sugar cane cannot.

• Sugar cane is recently living organic matter whereas coal is formed over millions of years.

• Sugar cane is a natural resource whereas coal is not.

The correct equation for the incomplete combustion of ethanol is:

• C_²H₅OH(l) + 1/2 O₂(g) → 2CO(g) + 3H₂(g)

• C₂H₅OH(l) + 3/2 O₂(g) → 2CO₂(g) + 3H₂(g)

• C₂H₅OH(l) + 2O₂(g) → 2CO(g) + 3H₂O(l)

• 
  C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l)

A reversible reaction has an enthalpy change, ΔH, of –50 kJ mol^–1 for the forward reaction.

Which one of the following pairs of energy profile diagrams, one for the forward reaction and one for the reverse reaction, represents this reaction?

• A

• B

• C

• D

Consider all of the components involved in the production of biofuels. The most accurate statement about all biofuels is that they:

• are not sustainable sources of energy.

• produce greenhouse gas emissions when burnt.

• produce the same amount of energy per unit of mass as fossil fuels.

• 
  release less carbon dioxide per unit of energy produced than fossil fuels.

Which one of the following statements about fuels is correct?

• Petroleum gas is a form of renewable energy.

• Electricity can only be generated by burning coal.

• Carbon dioxide is not produced when biogas is burnt.

• Biodiesel can be derived from both plant and animal material.

Which one of the following statements is correct?

• Crude oil can be classified as a biofuel because it originally comes from plants.

• 
  Methane, CH₄, can be classified as a fossil fuel because it has major environmental impacts.

• 
  Ethanol, CH₃CH₂OH, can be classified as a fossil fuel because it can be produced from crude oil.

• Hydrogen, H₂, can be classified as a biofuel because, when it combusts, it does not produce carbon dioxide, CO₂.

Consider the following energy profile for a particular chemical reaction, where I, II and III represent enthalpy changes during the reaction.

Which one of the following statements is correct?

• The activation energy for the reverse reaction is (III–II)

• The activation energy for the reverse reaction is (III–II)

• The energy required to break the reactant bonds is represented by II

• The energy released by the formation of new bonds is represented by I

Which one of the following statements is correct?

• Crude oil is formed from organic matter.

• Biodiesel has the same chemical formula as petrodiesel.

• Ethanol can only be produced from renewable material.

• When combusted, coal releases more energy per gram than coal seam gas.

Below is an energy profile diagram for an uncatalyzed reversible reaction.

A catalyst was added to the system, causing the rate of the forward and reverse reactions to increase. Which one of the following could be true for the catalyzed reaction?

• The activation energy to produce 1 mol of W is 29 kJ.

• The activation energy to produce 1 mol of Z is 12 kJ.

• The activation energy to produce 0.5 mol of X is 5 kJ.

• The activation energy to produce 9 mol of Y is 120 kJ.