Chapter 5: Energy from Combustion

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These questions cover Chapter 5 – all sections

Total point value for this assignment = 50 pts (a combination of completion and correctness)

1. List five fuels.

a. Name at least two properties that these fuels share.

b. Of the fuels you listed, which are fossil fuels or derived from them?

c. Of the fuels you listed, which are renewable?

2. Although coal is an important fuel for producing electricity, it also has drawbacks. Name three of these.

3. Mercury (Hg) is present in trace amounts in coal, ranging from 50–200 ppb.

Ýour Turn 5.19 mentions that 1.5 million tons of coal can be burned by a single power plant.

Using the formula: C135H96O9NS

a. What is the formula mass for this approximation of coal? ( in grams/mole)

b. Calculate tons of mercury in the coal based on the lower (50 ppb) concentrations

4. Name two ways in which all hydrocarbons are alike.

a. Then name two ways in which they differ.

5. Explain why cracking is a necessary part of the refinement of crude oil.

6. Octane ratings measure a fuel’s ability to minimize or prevent engine knocking. Why is this important?

a. A premium gasoline available at most stations has an octane rating of 91. What does this tell you about whether the fuel contains oxygenates?

7. The energy of sunlight can be converted into the potential (chemical) energy of glucose and oxygen.

a. Name the process by which this conversion occurs.

b. Name three fuels whose energy originates in sunlight.

8. What is a biofuel? Give 3 examples

9. Coal– burning power plants are responsible for two thirds of the sulfur dioxide emissions and one fifth of the nitrogen monoxide emissions. Hint: Revisit Chapter 2.

a. Why does burning coal produce SO2?

b. Name another source of SO2 in the atmosphere.

c. Why does burning coal produce nitrogen monoxide?

d. Name two other sources of NO.

10. Figure 5.10 is show below; depicts an electric power plant. Identify where: a. Potential (chemical) energy of the fuel is converted to heat. b. Kinetic energy of water molecules is converted to mechanical energy. c. Mechanical energy is converted to electrical energy. d. Electrical energy is converted into forms such as heat and light. 11. Use the bond energies in Table 5.1 to calculate the energy changes associated with the following: a. N2 the energy necessary to break the triple bond of a mole of nitrogen molecules b. H2 the energy necessary to break the triple bond of a mole of nitrogen molecules c. NH3 the energy released when the N-H bonds are formed (3 bonds per molecule) d. for the following reaction, what would be the overall energy: N2 (g) + 3 H2(g) 2 NH3(g) e. Would this reaction be considered endothermic or exothermic? 12. A 16.9-oz serving of a soft drink has an energy equivalent of 125 kcal. In kilojoules, what is the energy released when metabolizing this beverage? 13. During petroleum distillation, kerosene and hydrocarbons with 12–18 carbons used for diesel fuel condense at position C marked on this diagram. a. Separating hydrocarbons by distillation depends on differences in a specific physical property. Which one? b. How does the number of carbon atoms in the hydrocarbon molecules separated at A, B, and D compare with those separated at position C? Explain your reasoning. c. How do the uses of the hydrocarbons separated at A, B, and D differ from those separated at position C? Explain your reasoning. 14. The complete combustion of methane is given in Equation 5.4 a. By analogy, write the balance chemical equation for the combustion of ethane, C2H6 b. The heat of combustion for ethane, C2H6, is 52kJ/gram. How much heat is produced if 1.0 mol of ethane undergoes complete combustion? 15. State whether these processes are endothermic or exothermic. a. Charcoal burns in an outdoor grill. b. Water evaporates from your skin. c. Glucose is synthesized in the leaves of a plant by photosynthesis.