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 35 of 37
- A. Enthalpy of formation
- B. Enthalpy of combustion
- C. Enthalpy of neutralization
- D. Enthalpy of sublimation
Explanation: The enthalpy of formation is the standard reaction enthalpy for the formation of the compound from its elements (atoms or molecules) in…
Correct answer: Enthalpy of formation- A. Enthalpy of combustion
- B. Enthalpy of solution.
- C. Enthalpy of formation
- D. Enthalpy of atomization
Explanation: Combustion reactions release heat, so the enthalpy change of the system, H, will always be negative.
Correct answer: Enthalpy of combustion- A. ΔG
- B. ΔH
- C. ΔE
- D. ΔH-ΔE
Explanation: Enthalpy change is the heat absorbed by a substance at constant pressure. ΔH= ΔU + PΔV= Q - PΔV + PΔV = Q
Correct answer: ΔH684. ΔH is the difference in the number of moles of reactants and products in a reaction which is _.
- A. Solid phase
- B. Liquid phase
- C. Gaseous phase
- D. Plasma phase
Explanation: ∆n is equal to the total moles of gas on the products side - total moles of gas on the Reactant side.
Correct answer: Gaseous phase- A. Energy released in bond breaking is greater
- B. Energy released in bond making is greater
- C. Energy absorbed in bond breaking is greater
- D. Energy absorbed In bond making is greater
Explanation: Breaking these bonds requires energy to be absorbed by the reaction. But then, new bonds form between hydrogen and oxygen and between…
Correct answer: Energy released in bond making is greater- A. Exothermic reaction
- B. Endothermic reaction
- C. Spontaneous reaction
- D. Non-spontaneous reaction
Explanation: During the enthalpy change of the solution of Na2CO3 , the temperature of the solvent rises showing that the process is exothermic.
Correct answer: Exothermic reaction- A. Exothermic
- B. Endothermic
- C. Spontaneous
- D. Non-spontaneous
Explanation: The enthalpy change of solution of sodium carbonate is -24.6kJ.mol-1. Since enthalpy change is negative, the reaction is exothermic.
Correct answer: Exothermic- A. More than 1
- B. Positive
- C. Negative
- D. Neutral
Explanation: Exothermic reaction is a reaction in which net energy is released in a reaction.
Correct answer: Negative- A. 74 J
- B. 10 J
- C. 116 J
- D. 106 J
Explanation: The change in internal energy (ΔU) can be calculated using the first law of thermodynamics: ΔU = Q - W Where: * ΔU is the change in…
Correct answer: 10 J- A. Second law of thermodynamics
- B. Third law of thermodynamics
- C. First law of thermodynamics
- D. Zeroth law of thermodynamics
Explanation: The law of conservation of energy states that the energy is always conserved in a closed system.
Correct answer: First law of thermodynamics- A. Equal to reactants
- B. More than reactants
- C. Always zero
- D. Less than reactants
Explanation: The total energy of products in a chemical reaction are equal to reactants according to the law of conservation of energy, which states…
Correct answer: Equal to reactants- A. +878 kJ mol-1
- B. -1942 kJ mol-1
- C. -878 kJ mol-1
- D. -2474 kJ mol-1
Explanation: The explanation for this question will be added soon.
Correct answer: -878 kJ mol-1- A. Joule's law
- B. Law of conservation of energy
- C. Hess's law
- D. Henry's law
Explanation: According to Hess's law, the thermal effects of a reaction depends upon the initial and final conditions of the reacting substances.
Correct answer: Hess's law- A. Work done
- B. Internal energy change
- C. Enthalpy
- D. Entropy
Explanation: At constant volume, the heat of the reaction is equal to the 'change in the internal energy of the system'.
Correct answer: Internal energy change- A. System
- B. Surroundings
- C. Boundary
- D. None of these options are correct
Explanation: The substance within the cylinder is the system and cylinder itself, piston and everything outside the cylinder is a part of the…
Correct answer: Surroundings- A. Amount of heat added to the system
- B. Amount of heat rejected from the system
- C. Temperature of the substance
- D. Amount of the substance
Explanation: Enthalpy change is a state function so it does not depend on the path taken by the reaction.
Correct answer: Amount of the substance- A. 4.18 J/g/0C
- B. 9.82 J/g/0C
- C. 6.04 J/g/0C
- D. 8.47 J/g/0C
Explanation: Water's specific heat power is 4.2 joules per gram per Celsius degree or 1 calorie per gram per Celsius degree.
Correct answer: 4.18 J/g/0C- A. 4.184J
- B. 4.184 kJ
- C. 0.4184J
- D. 0.4184kJ
Explanation: Since 1925 this calorie has been defined in terms of the joule, the definition since 1948 being that one calorie is equal to approximately…
Correct answer: 4.184J- A. Pressure (P)
- B. Work(W)
- C. Volume (V)
- D. Temperature (T)
Explanation: Work is not an state function. It is a pathway function
Correct answer: Work(W)- A. Surrounding
- B. System
- C. Confined space
- D. None of these options are correct
Explanation: In chemistry, the term "surroundings" refers to everything outside of the system being studied.
Correct answer: System