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 8 of 37
- A. P
- B. V
- C. q
- D. H (enthalpy)
Explanation: A state function is a property of a system that depends only on the current state of the system, not on the path by which the system…
Correct answer: q- A. +q, +w, +E
- B. -q, -w, +E
- C. +q, -w, - E
- D. -q, +w, -E
Explanation: In thermodynamics, the standard sign convention is that energy added to a system in the form of heat is treated as positive, and energy…
Correct answer: +q, -w, - E- A. 78 g
- B. 110 g
- C. 370 g
- D. 1100 g
Explanation: Now, the molar mass of water (H2O) is approximately 18.015 g/mol.The mass of ice (in grams) required to absorb this energy is:mass of ice…
Correct answer: 1100 g- A. 3H2(g) + N2(g) → 2NH3(g)
- B. 2NH3(g) → 3H2(g) + N2(g)
- C. 3/2 H2(g) + 1/2 N2(g) → NH3(g)
- D. NH3(g) → 3/2 H2(g) + 1/2 N2(g)
Explanation: The standard enthalpy of formation (ΔH°f) of a compound is the enthalpy change when one mole of the compound is formed from its…
Correct answer: 3H2(g) + N2(g) → 2NH3(g)- A. H2O(s) → H2O(l)
- B. 2H2O(g) → 2H2(g) + O2(g)
- C. H2O(g) → H2O(l)
- D. Al2O3(l) + 2Fe(l) → 2Al(s) + Fe2O3(s)
Explanation: An endothermic reaction is a chemical reaction that absorbs heat from its surroundings, resulting in an increase in the internal energy of…
Correct answer: H2O(g) → H2O(l)- A. Hvaprizaiton < Hsublimation < Hfusion < Hcondensation
- B. Hfusion < Hcondensation < sublimation < Hvaporization
- C. Hcondensation < Hfusion < Hvaporization < Hsublimation
- D. Hcondensation < Hsublimation < Hfusion < Hvaporization
Explanation: This order is generally correct. Vaporization typically requires more energy than sublimation, which requires more energy than fusion…
Correct answer: Hvaprizaiton < Hsublimation < Hfusion < Hcondensation- A. -102.4 kJ
- B. -322.1 kJ
- C. -373.3 kJ
- D. -400.0 kJ
Explanation: Let's calculate the enthalpy of the given reaction using Hess's Law. We'll use the enthalpies of the provided reactions to find the…
Correct answer: -400.0 kJ- A. -800 J
- B. -400 J
- C. O J
- D. +400J
Explanation: The change in internal energy (AU) of a system is given by the difference between the heat added to the system (q) and the work done by…
Correct answer: -800 J- A. continue to occur once started
- B. require activation energy
- C. are endothermic
- D. are exothermic
Explanation: Spontaneous reactions are those that proceed without any external intervention once initiated.
Correct answer: continue to occur once started- A. reaction of H2 with O2 to form H2O
- B. combustion of natural gas
- C. neutralization of HCI by NaOH
- D. synthesis of glucose by plants
Explanation: The process that is not spontaneous among the given options is:d. synthesis of glucose by plantsThe synthesis of glucose by plants, also…
Correct answer: synthesis of glucose by plants- A. chemical processes
- B. physical processes
- C. biochemical processess
- D. endothermic processes
Explanation: Sublimation, vaporization, melting, and photosynthesis are all examples of different physical processes.Sublimation refers to the process…
Correct answer: physical processes- A. water will vaporize
- B. ice will sublime
- C. ice will melt
- D. water will freeze
Explanation: This is correct because the amount of heat energy removed can melt approximately 0.18 g of ice.To determine what happens when 60J of heat…
Correct answer: ice will melt- A. Ti
- B. AI
- C. w
- D. Na
Explanation: The enthalpy of fusion (also known as heat of fusion) is the amount of heat required to change a substance from a solid to a liquid at its…
Correct answer: w- A. internal energy of the system increases and no work is done on the surrounding
- B. internal energy of the system increases and work is done on the surrounding
- C. no change in internal energy occurs
- D. no work is done on the surrounding
Explanation: When the volume of a system is kept constant, the process is called isovolumic or constant volume.
Correct answer: internal energy of the system increases and no work is done on the surrounding- A. spontaneous exothermic process
- B. spontaneous endothermic process
- C. non-spontaneous exothermic process
- D. non-spontaneous endothermic process
Explanation: The melting of ice at room temperature involves the transition of solid ice into liquid water.
Correct answer: spontaneous endothermic process- A. v
- B. -ive
- C. 0
- D. +ive or -ive
Explanation: ΔH neutralization refers to the enthalpy change associated with a neutralization reaction, which occurs when an acid reacts with a base to…
Correct answer: -ive- A. Dissolution of NH4Cl in excess of water is an endothermic process
- B. Neutralization is always exothermic
- C. The absolute value of enthalpy (H) can be determined experimentally
- D. The heat of reaction at constant volume is denoted by ΔE
Explanation: Neutralization reactions involve the combination of an acid and a base to form water and a salt.
Correct answer: Neutralization is always exothermic- A. Exothermic
- B. Endothermic
- C. May or may not be Exothormic or Endothermic
- D. None of these
Explanation: Explanation: A negative delta H value indicates an exothermic reaction, where heat is released to the surroundings.
Correct answer: Exothermic- A. delta H<0
- B. delta G<0
- C. delta S<0
- D. delta G>0
Explanation: Explanation: A spontaneous endothermic process has a negative change in Gibbs free energy (delta G<0), indicating that it can proceed…
Correct answer: delta G<0- A. Is spontaneous.
- B. Spontaneity is temperature dependent.
- C. Has an increasing free energy
- D. Is non-spontaneous
Explanation: Explanation: Whether the reaction is spontaneous or not depends on the temperature, as it influences the sign of delta G through the…
Correct answer: Spontaneity is temperature dependent.