Unit 3 Exam revision

Select the correct statement about the heat of combustion of methane compared to pentane.

• It is not predictable how the heat of combustion of pentane will compare to methane.

• Pentane will have a lower energy density but a higher molar heat of combustion.

• Pentane will have a higher energy density and a higher molar heat of combustion.

• The heat of combustion of all alkanes is the same as the bonds are similar.

Use the following information to answer Questions 2 and 3. A container of ethane has a volume of 496 litres. The contents are at SLC. The ethane is burnt in excess oxygen gas. The energy released by the ethane will be

• 312 kJ

• 6.12 × 102 kJ

• 3.12 × 104 kJ

• 2.58 × 104 kJ

Use the following information to answer Questions 2 and 3. A container of ethane has a volume of 496 litres. The contents are at SLC. The ethane is burnt in excess oxygen gas. The mass of carbon dioxide produced will be

• 240 g

• 880 g

• 1240 g

• 1760 g

Which of the following waste products is most likely to be used to produce bioethanol?

• Grape juice residues

• Used fish and chip oil

• Waste from a sunflower crop

• Waste from a pig farm

The energy required to convert water to steam is shown below. H2O(l) → H2O(g) ΔH = +41 kJ mol⁻¹ Using the equation above, the value of ΔH for the reaction CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) is

• -41 kJ mol⁻¹

• -808 kJ mol⁻¹

• +849 kJ mol⁻¹

• -849 kJ mol⁻¹

An energy profile diagram is shown below: The activation energy and the ΔH value for the reverse reaction will be, respectively,

• +400 kJ mol⁻¹ and +600 kJ mol⁻¹

• +600 kJ mol⁻¹ and -400 kJ mol⁻¹

• +1000 kJ mol⁻¹ and +600 kJ mol⁻¹

• -1000 kJ mol⁻¹ and -600 kJ mol⁻¹

Nitrogen monoxide gas can react with oxygen to form brown NO2 gas in a reversible reaction. 2NO(g) + O2(g) ⇌ 2NO2(g) ΔH = -114 kJ mol⁻¹. Extra oxygen gas is injected into an equilibrium sample of the above gases. The impact of this addition will

• lead to an increase in the temperature in the reactor.

• have no impact on the rate of the forward reaction.

• have no impact on the pressure in the reactor.

• lead to a decrease in temperature of the reactor.

A change is made to a different equilibrium mixture of the above gases and the brown intensity in the reactor is seen to decrease. The change made was not

• a decrease in volume of the reactor.

• an increase in volume of the reactor.

• a decrease in temperature.

• the addition of an inert gas to the mixture.

Caprylic acid, shown below, is a component of milk. The molecular formula of the biodiesel molecule formed from the reaction between caprylic acid and methanol will be

• C9H18O2

• C8H18O2

• C9H16O2

• C9H20O2

A pathway to form the molecule below could be

• ethane + methanamine in the presence of UV light.

• propene + steam with acid as a catalyst, then the addition of ammonia.

• propane + chlorine with UV light as a catalyst, then the addition of ammonia.

• butane + chlorine with UV light as a catalyst, then the addition of ammonia.