Free Thermochemistry and Energetics of Chemical Reactions MCQs with Answers
728 Thermochemistry and Energetics of Chemical Reactions MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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728 questions · page 4 of 37
- A. pressure
- B. temperature
- C. enthalpy
- D. all of the above
Explanation: Pressure, temperature and enthalpy are all state functions because their values depend only on the present state of the system, not on how…
Correct answer: all of the above- A. spontaneous process
- B. non-spontaneous process
- C. irreversible process
- D. reversible process
Explanation: Water does not move uphill by itself because increasing gravitational potential energy requires energy supplied from outside, so pumping…
Correct answer: non-spontaneous process- A. environment
- B. surrounding
- C. state function
- D. enthalpy
Explanation: A state function is a property whose change depends only on the initial and final states, so the path of the process does not affect its…
Correct answer: state function- A. State function
- B. phase
- C. surrounding
- D. state
Explanation: The surroundings are everything outside the system that can exchange energy or matter with it.
Correct answer: surrounding- A. Internal energy
- B. Enthalpy
- C. Gibbs free energy
- D. Work
Explanation: Internal energy, enthalpy and Gibbs free energy depend only on the state of the system, so they are state functions.
Correct answer: Work- A. Hydrazine
- B. Both have equal enthalpy of formation
- C. Hydrogen gas
- D. Cannot be compared
Explanation: The performance of rocket fuel is measured by its enthalpy of combustion, which is the amount of heat released when one mole of the fuel…
Correct answer: Hydrogen gas- A. Enthalpy
- B. Surrounding
- C. Work
- D. Internal energy
Explanation: internal energy is equal to enhalpy change and work doneH=E+PV
Correct answer: Internal energy- A. Delta*H_{v} > Delta*H_{f}
- B. Delta*H_{s} > Delta*H_{f}
- C. Delta*H_{f} > Delta*H_{r}
- D. Delta*H_{x} > Delta*H_{v}
Explanation: deltaHf is less than deltaHr because in formation only specific product with one mole forms but in reaction all type of reaction are…
Correct answer: Delta*H_{f} > Delta*H_{r}- A. Evolved
- B. Absorbed
- C. Either Evolved or Absorbed
- D. None of the above
Explanation: The heat of formation, also known as the standard enthalpy of formation, is the heat change accompanying the formation of one mole of a…
Correct answer: Either Evolved or Absorbed- A. Heat of formation of one mole of salt
- B. Heat of formation of one mole of water
- C. Both a and b
- D. None of these
Explanation: The heat of neutralization is defined as the heat change that occurs when one mole of water is formed by the combination of an acid and a…
Correct answer: Heat of formation of one mole of water- A. Change in internal energy (ΔE)
- B. Change in enthalpy (ΔH)
- C. Change in free energy (ΔG)
- D. Change ín temperature only (ΔT)
- E. Change in pressure only (ΔP)
Explanation: At constant pressure, the heat of reaction is equal to the enthalpy change of the system.
Correct answer: Change in enthalpy (ΔH)- A. 3.426 kJ
- B. 13.7 kJ
- C. 5.2 kJ
- D. 55 kJ
Explanation: The balanced chemical equation for the neutralization is: H2SO4(aq) + 2KOH(aq) → K2SO4(aq) + 2H2O(l).
Correct answer: 3.426 kJ- A. 379 kJ
- B. 215 kJ
- C. 208 kJ
- D. 315 kJ
Explanation: First, convert the mass of CO₂ to moles: 35.2 g / 44 g/mol = 0.8 mol. The heat released is then the number of moles multiplied by the…
Correct answer: 315 kJ- A. 100 gm
- B. 180 gm
- C. 200 gm
- D. 120 gm
Explanation: Work(W) = m * g * h Where: m = mass of the person = 100kg g = acceleration due to gravity = 10 m/s^2 h = height of the hill = 500meters W…
Correct answer: 120 gm- A. 1238.78 J mol−1
- B. −2477.57 J mol−1
- C. 2477.57 J mol−1
- D. −1238.78 J mol−1
Explanation: C(s) + ½O(g) → CO(g) ∆H = ∆U + ∆ngRT (∆H − ∆U) = ∆ngRT= 1/2 x 8.314 x 298 = −1238.78 J mol−1
Correct answer: −1238.78 J mol−1- A. endothermic
- B. exothermic
- C. ∆H = 0
- D. none of the above
Explanation: ∆H = (∆Hf°)Products - (∆Hf°)Reactants = 3 × (- 393.7) - 2 × (-824.2) = 476.3 kJ/mole (remember the formula for further use)
Correct answer: endothermic- A. 20 ml acid and 30 ml alkali
- B. 10 ml acid and 40 ml alkali
- C. 25 ml acid and 25 ml alkali
- D. 35 ml acid and 15 ml alkali
Explanation: When 25 ml acid reacts with 25 ml of alkali, maximum equivalent of acid is reacting with alkali.
Correct answer: 25 ml acid and 25 ml alkali- A. Heat of combustion
- B. Heat of formation
- C. Heat of solution
- D. Heat of dilution
Explanation: The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of…
Correct answer: Heat of formation79. The change in heat energy in a chemical reaction at constant temperature and pressure is called:
- A. Enthalpy change
- B. Heat of sublimation
- C. Internal energy change
- D. Heat of formation
Explanation: The change in heat energy in a chemical reaction at constant temperature and pressure is called enthalpy change.
Correct answer: Enthalpy change80. What is the value of enthalpy of neutralization when one mole of base reacts with one mole of acid?
- A. -60.5 kJ/mol
- B. -46.5kJ/mol
- C. -70.5 kJ/mol
- D. -57.4kJ/mol
Explanation: Option A: This option suggests a value of -60.5 kJ/mol for the enthalpy of neutralization.
Correct answer: -57.4kJ/mol