Questions about Heat of Combustion
Multiple-Choice Questions: Heat of Combustion
1. What is the heat of combustion?
A) The energy released when a compound melts
B) The energy absorbed during a chemical reaction
C) The heat released when one mole of a substance burns completely in oxygen
D) The heat required to vaporize a liquid
E) The heat absorbed during freezing
2. The heat of combustion is usually expressed in units of:
A) Joules per mole (J/mol)
B) Celsius (°C)
C) Moles per liter (mol/L)
D) Atmospheres (atm)
E) Meters (m)
3. Which of the following is true about the heat of combustion?
A) It is always positive
B) It is always negative
C) It can be positive or negative depending on the compound
D) It depends only on temperature, not on the substance
E) It depends only on pressure
4. The heat of combustion of a hydrocarbon is typically:
A) Small and positive
B) Large and negative
C) Zero
D) Positive and large
E) Negative and zero
5. The heat of combustion is an example of:
A) Endothermic process
B) Exothermic process
C) Isothermal process
D) Adiabatic process
E) Photochemical reaction
6. In what state are the reactants and products typically considered when measuring standard heat of combustion?
A) Solid reactants and liquid products
B) Gaseous reactants and liquid products
C) Standard state conditions (usually 1 atm and 25°C)
D) High pressure and temperature conditions
E) Plasma state
7. Which of the following affects the heat of combustion of a compound?
A) Molecular structure
B) Amount of oxygen available
C) Presence of catalysts
D) Temperature and pressure conditions
E) All of the above
8. The heat of combustion is important in:
A) Determining the energy content of fuels
B) Calculating boiling points
C) Predicting solubility in water
D) Measuring density
E) Estimating reaction rates
9. The heat of combustion of methane (CH₄) is approximately:
A) +890 kJ/mol
B) -890 kJ/mol
C) 0 kJ/mol
D) -444 kJ/mol
E) +444 kJ/mol
10. When a fuel burns completely, the heat of combustion is:
A) The amount of heat absorbed from the surroundings
B) The amount of heat released to the surroundings
C) Always zero
D) Independent of the type of fuel
E) Equal to the boiling point of the fuel
11. Which device is commonly used to measure heat of combustion experimentally?
A) Spectrophotometer
B) Bomb calorimeter
C) Gas chromatograph
D) Mass spectrometer
E) Thermocouple
12. In a bomb calorimeter, the heat of combustion is measured under:
A) Constant pressure
B) Constant volume
C) Constant temperature
D) Constant mass
E) Vacuum conditions
13. If the heat of combustion of a substance is very high (in magnitude), the substance is:
A) A poor fuel
B) A good fuel
C) Non-flammable
D) A solid at room temperature
E) Water-soluble
14. The heat of combustion for octane (C₈H₁₈), a gasoline component, is roughly:
A) -5470 kJ/mol
B) -547 kJ/mol
C) +5470 kJ/mol
D) +547 kJ/mol
E) 0 kJ/mol
15. How is the heat of combustion related to fuel efficiency?
A) Higher heat of combustion means lower fuel efficiency
B) Lower heat of combustion means higher fuel efficiency
C) Higher heat of combustion means more energy per mole, thus higher efficiency
D) Heat of combustion is unrelated to fuel efficiency
E) Heat of combustion only matters for non-fuel substances
16. Which of these compounds is expected to have the highest heat of combustion per mole?
A) Methane (CH₄)
B) Ethane (C₂H₆)
C) Propane (C₃H₈)
D) Butane (C₄H₁₀)
E) Octane (C₈H₁₈)
17. Heat of combustion values are most often given for:
A) Liquids only
B) Gases only
C) Solids only
D) Pure substances in their standard states
E) Mixtures
18. The standard heat of combustion of a compound is negative because:
A) Energy is required to break bonds
B) Energy is released when new bonds form in the products
C) Heat is absorbed from surroundings
D) The reaction is non-spontaneous
E) The reaction occurs at low temperatures
19. Which of the following is NOT true about heat of combustion?
A) It helps in designing fuels and engines
B) It can be used to calculate the enthalpy change of formation
C) It measures the heat released when a compound freezes
D) It is a key parameter in energy industries
E) It is related to the complete oxidation of a fuel
20. The difference between higher heating value (HHV) and lower heating value (LHV) relates to:
A) The presence of moisture in the fuel
B) The energy content including or excluding latent heat of vaporization of water
C) The amount of carbon in the fuel
D) The temperature at which combustion occurs
E) The pressure of combustion
- Questions about Heats of Vaporization and Condensation
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Answers
1. C
2. A
3. B
4. B
5. B
6. C
7. E
8. A
9. B
10. B
11. B
12. B
13. B
14. A
15. C
16. E
17. D
18. B
19. C
20. B
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