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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- A. State of the system may change
- B. Temperature of the system may change
- C. Chemical reaction may take place
- D. Route of the system may change
Explanation: When the internal energy of a system increases, several changes can indeed take place, but the "route" of the system is not one of them.
Correct answer: Route of the system may change- A. Increase in enthalpy
- B. Decrease in enthalpy
- C. No change in enthalpy
- D. Decrease in internal energy
Explanation: When a solid melts and transforms into a liquid, it requires an input of energy to break the intermolecular forces and allow the particles…
Correct answer: Increase in enthalpy- A. Heat of combustion
- B. Heat of decomposition
- C. Heat of solution
- D. Heat of reaction
Explanation: The correct option is D) Heat of reaction. The ∆Hf (enthalpy of formation) of a compound is equal in magnitude to the heat of reaction.
Correct answer: Heat of reaction- A. High
- B. Low
- C. Zero
- D. One
Explanation: Based on the usual behavior of heat of solution for common ionic compounds like NaCl, the correct option is B) Low.
Correct answer: Low- A. Internal energy
- B. Temperature of a body
- C. Kinetic energy
- D. Heat energy
Explanation: Thermal energy also called heat energy is produced when a rise in temperature causes atoms and molecules to move faster and collide with…
Correct answer: Heat energy- A. Law of mass action
- B. Law of conservation of energy
- C. Law of conservation of mass
- D. Dalton's law of partial pressure
Explanation: Hess's law is based on the principle of the conservation of energy. It states that the total enthalpy change of a chemical reaction is…
Correct answer: Law of conservation of energy- A. Heat lost by the system
- B. Work done on the system
- C. Work done by the system
- D. Positive ∆E when heat is lost by the system
Explanation: Work done on the system is positive. When work is done on the system, it means that energy is being transferred into the system.
Correct answer: Work done on the system- A. Exothermic process
- B. Endothermic process
- C. Neutral
- D. Energy wasted
Explanation: When an electron is removed from an atom, it requires an input of energy to overcome the electrostatic attraction between the electron and…
Correct answer: Endothermic process- A. Endothermic reactions
- B. Exothermic reactions
- C. Endergonic reactions
- D. Heat gaining reactions
Explanation: Exothermic reactions are the reactions that release heat to their surroundings, causing the surroundings to warm up while the system loses…
Correct answer: Exothermic reactions- A. 4.98 J
- B. 7.98 J
- C. 4.18 J
- D. 8.21 J
Explanation: One calorie is approximately equal to 4.18 joules. This conversion factor is used to convert energy measurements between the calorie…
Correct answer: 4.18 J- A. 1st law
- B. 2nd law
- C. 3rd law
- D. None of these
Explanation: The first law of thermodynamics, also known as the Law of Energy Conservation, states that energy cannot be created or destroyed; it can…
Correct answer: 1st law- A. Electrochemistry
- B. Biochemistry
- C. Thermochemistry
- D. Analytical chemistry
Explanation: The study of chemical reactions involving change in heat energy is called thermochemistry.
Correct answer: Thermochemistry- A. -60.5 KJ/mol
- B. -46.5 KJ/mol
- C. -70.5 KJ/mol
- D. -57.4KJ/mol
Explanation: The enthalpy of neutralization when one mole of strong base reacts with one mole of strong acid is approximately -57.1 kJ/mol.
Correct answer: -57.4KJ/mol- A. Hess's law
- B. Carnot cycle
- C. Born Haber cycle
- D. Haber's process
Explanation: The enthalpy cycle used to calculate the lattice energy is called the Born-Haber cycle.The Born-Haber cycle is a thermochemical cycle that…
Correct answer: Born Haber cycle- A. Enthalpy of formation
- B. Enthalpy of neutralization
- C. Enthalpy of sublimation
- D. Enthalpy of reaction
Explanation: The change in enthalpy for the reaction NaOH + HCl → NaCl + H2O is called the enthalpy of neutralization.The enthalpy of neutralization is…
Correct answer: Enthalpy of neutralization- A. Heat
- B. Work
- C. Heat & work
- D. Force
Explanation: Heat is the transfer of thermal energy between a system and its surroundings due to a temperature difference.
Correct answer: Heat & work- A. Microscopic
- B. Dependent
- C. Macroscopic
- D. Constant
Explanation: A state function is a macroscopic property of a system. It is a property that depends only on the current state of the system and not on…
Correct answer: Macroscopic- A. Exothermic reaction
- B. Endothermic reaction
- C. Spontaneous reaction
- D. Non-spontaneous reaction
Explanation: An exothermic reaction releases heat energy into its surroundings. During combustion, substances typically release heat, making the heat…
Correct answer: Exothermic reaction- A. Solid phase
- B. Gases phase
- C. Liquids, solids and solution
- D. None of these
Explanation: In many cases involving reactions in liquids, solids, or solutions, the differences between ΔH and ΔE are relatively small.
Correct answer: Liquids, solids and solution- A. Thermal energy
- B. Total heat content
- C. Internal energy
- D. Enthalpy
Explanation: The sum of all the energies present in a reaction mixture or system is called the "internal energy" (U).
Correct answer: Internal energy