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 20 of 37
- A. Average translational kinetic energy
- B. Average rotational kinetic energy
- C. Average translational potential energy
- D. Average vibrational kinetic energy
Explanation: Heat flow between hotter and colder gases continues until all the molecules have an equal average translational kinetic energy due to the…
Correct answer: Average translational kinetic energy- A. 35-50°C
- B. 130-150°C
- C. 400-450°C
- D. 500-600°C
Explanation: Option C is correct. The optimum temperature for the Haber process is 400-450°C.
Correct answer: 400-450°C- A. Jg-1K-1
- B. JK-1
- C. JmolK-1
- D. KJ/mol
Explanation: The correct answer is Jg-1K-1, which is the SI unit of specific heat capacity.
Correct answer: Jg-1K-1- A. 4.2 kJ/mol/K
- B. 4.2 j/g.K
- C. 4.61/g/K
- D. 42/g/K
Explanation: The specific heat capacity of water is approximately 4.2 joules per gram per degree Celsius (J/g/°C).
Correct answer: 4.2 j/g.K- A. E = q+w
- B. E = q+(-w)
- C. E= (-q)+(-w)
- D. E = (-q)+w
Explanation: According to the first law of thermodynamics:ΔE=q+wq = heat absorbed by the system (positive if absorbed, negative if released)w= work…
Correct answer: E = q+(-w)- A. Equal to delta H
- B. More than delta H
- C. Less than delta H
- D. Zero
Explanation: For an endothermic reaction, the enthalpy of reaction (ΔH) is positive, indicating that energy is absorbed during the reaction.
Correct answer: More than delta H387. Amount of heat absorbed, when one mole of liquid changes to gas at its boiling point is called:
- A. Molar heat of sublimation
- B. Heat of vaporisation
- C. Latent heat of fusion
- D. Heat capacity
Explanation: The heat of vaporization is the amount of heat energy required to change one mole of a liquid into a gas at its boiling point, without any…
Correct answer: Heat of vaporisation- A. Diamond
- B. Graphite
- C. Peat
- D. Coa
Explanation: Graphite - Correct. Graphite is the most stable allotrope of carbon due to its lower Gibbs free energy.
Correct answer: Graphite- A. Henry's law
- B. Second law of thermodynamics
- C. First law of thermodynamics
- D. Second law of thermochemistry
Explanation: First law of thermodynamics - Correct. Hess's law is based on the conservation of energy, which aligns with the first law.
Correct answer: First law of thermodynamics- A. Combustion of methane
- B. Decomposition of water
- C. Dehydrogenation of ethane or ethylene
- D. Conversion of graphite
Explanation: Combustion of methane releases energy, making it an exothermic reaction.
Correct answer: Combustion of methane- A. ΔE+W
- B. qv = E +PΔV
- C. qv= E+W
- D. qv = E
- E. qv = PΔGV
Explanation: The equation of the first law of thermodynamics, q = ΔE + W, reduces at constant volume to qv = ΔE.At constant volume (no work is done)…
Correct answer: qv = E- A. Second order
- B. First order
- C. Half order
- D. Third order
- E. Zero order
Explanation: The correct answer is e) Zero order. The given reaction H2 + Cl2 -> 2HCl is a zero-order reaction, where the reaction rate is independent…
Correct answer: Zero order- A. Lussac's law of combining volume
- B. Hess's law
- C. Boyle's law
- D. Charle's law
- E. Avagadro's law
Explanation: Hess's law states that the enthalpy change of a reaction is independent of the pathway taken from reactants to products.
Correct answer: Hess's law- A. Same
- B. Sometimes decreases sometimes increases
- C. Reaction moves backward
- D. Decreases
- E. Increases
Explanation: In exothermic reactions Kc is inversely proportional to temperature it mean when temperature will increase Kc will decrease and when…
Correct answer: Increases- A. 0.0821 joules
- B. 8.314 dm3-atm
- C. 0.0821 KJ
- D. 0.0821 dm³-atm
Explanation: One mole of an ideal gas at 273.16 K and one atmospheric pressure and its temperature is increased by 1K, then it will absorb 0.0821…
Correct answer: 0.0821 dm³-atm- A. Henry's law
- B. Le - Chatleir's Principle
- C. Hess's law
- D. Common Ion effect
Explanation: The Born-Haber cycle is a thermodynamic cycle used to determine the lattice energy of ionic compounds, which is the energy required to…
Correct answer: Hess's law- A. Freezing
- B. Decomposition
- C. Sublimation
- D. Enthalpy
Explanation: Enthalpy is a state function. State functions are properties that depend only on the current state of a system and are independent of the…
Correct answer: Enthalpy- A. Refrigerant
- B. A solvent
- C. Insecticides
- D. A fire extinguisher
Explanation: Freon is commonly known as refrigerant. Refrigerants are substances used in refrigeration systems and air conditioning units to transfer…
Correct answer: Refrigerant- A. Isolated system
- B. Closed system
- C. Open system
- D. Adiabatic system
Explanation: An open system can exchange both energy and matter with its surroundings.
Correct answer: Open system- A. Specific heat
- B. Heat capacity
- C. Latent heat
- D. Internal energy
Explanation: Internal energy U of a system or a body with well-defined boundaries is the total of the kinetic energy due to the motion of molecules and…
Correct answer: Internal energy