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 36 of 37
- A. Initial conditions
- B. Final conditions
- C. Initial and final conditions
- D. Path of the reaction
Explanation: The change in volume of a system depends on either its pressure or temperature.
Correct answer: Initial and final conditions- A. Surrounding from the environment
- B. Reactants from contamination
- C. System from surrounding
- D. Products from surrounding
Explanation: The real or imaginary surface separating the 'system from the surrounding' is called the boundary.
Correct answer: System from surrounding- A. Water
- B. Cup
- C. Whole table
- D. All of these
Explanation: In the given situation, if the focus is on the water in the cup, then the system would be the water itself.
Correct answer: Water- A. System
- B. Surroundings
- C. Boundary
- D. None of these are correct
Explanation: A piston in a cylinder is part of the surrounding.
Correct answer: Surroundings- A. Analyte
- B. System
- C. Surrounding
- D. Boundary
Explanation: In thermodynamics, a system refers to the part of the universe that is being studied or analyzed.
Correct answer: System- A. ΔHv
- B. ΔHf
- C. ΔHi
- D. ΔHs
Explanation: The molar heat of fusion (ΔHfus) of a substance is the heat absorbed by one mole of that substance as it is converted from a solid to a…
Correct answer: ΔHf- A. MgCO3 + 2HCl → MgCl2 + CO2 + H2O
- B. KOH + HCl → KCl + H2P
- C. NH4Cl + NaOH → NaCl + H2O + NH3
- D. H2SO4 + Mg(OH)2 → MgSO4 + 2H2O
Explanation: The given reaction depicts a neutralization reaction, where one mole of acid is neutralized by one mole of alkali (as indicated by 1 mole…
Correct answer: H2SO4 + Mg(OH)2 → MgSO4 + 2H2O- A. 2 H2 (g) + O2 (g) -> 2H2O (l)
- B. C(s) + O2 (g) -> CO2(g)
- C. N2(g) + O2 (g) -> N2O2 (g)
- D. None of these
Explanation: Because heat is absorbed in this reaction. All the other reactions are exothermic as the heat is released during the process.
Correct answer: N2(g) + O2 (g) -> N2O2 (g)- A. H+(aq) + OH−(aq) -> H2O(l)
- B. 1/2 H2(g) -> H(g)
- C. Na(g) -> Na+(g) + 1e−
- D. 1/2 Cl2(g) -> Cl(g)
Explanation: Explanation:Neutralization is always an exothermic reaction. Hence, the correct answer is A.
Correct answer: H+(aq) + OH−(aq) -> H2O(l)- A. C(g) + O2(g) → CO2(g)
- B. N2(g) + 3H2(g) → 2NH3(g)
- C. 2H2O(l) → 2H2(g) + O2(g)
- D. None of the above
Explanation: Explanation:This reaction is endothermic reaction: 2H2O (l) → 2H2 + O2 This reaction is Exothermic reaction, not endothermic.
Correct answer: 2H2O(l) → 2H2(g) + O2(g)- A. Unidirectional and irreversible
- B. Irreversible and a real process
- C. Unidirectional and a real process
- D. All of the above
Explanation: A is incorrect because spontaneous process is also real processB is incorrect because spontaneous process is also unidirectionalC is…
Correct answer: All of the above- A. Constant Volume
- B. Constant Pressure and volume
- C. Variable pressure
- D. Constant pressure
Explanation: Enthalpy is a thermodynamic state function that represents the internal energy of a system plus the product of pressure and volume.
Correct answer: Constant pressure- A. 0.1
- B. 1.0
- C. 29.8
- D. Zero
Explanation: The correct answer is Zero. In thermodynamics, the standard enthalpy of formation for an element in its most stable form at 1 atm pressure…
Correct answer: Zero- A. △H = q + P△V
- B. △H = △E- P△V
- C. △H = △E + P△V
- D. △H = q - P△V
Explanation: The change in enthalpy, ∆H, at constant pressure is equal to the sum of the heat absorbed or released, q, and the pressure-volume work…
Correct answer: △H = q + P△V- A. Endothermic
- B. Exothermic
- C. Spontaneous
- D. Non spontaneous
Explanation: When the enthalpy of the reactants is greater than the enthalpy of the products, it means that the reaction releases more energy than it…
Correct answer: Exothermic- A. 𝚫H=𝚫E +P𝚫V
- B. 𝚫H=P𝚫V
- C. 𝚫H=𝚫E
- D. 𝚫H=0
Explanation: Option C is correct as ΔH=ΔE+PΔV and for a process involving solids and/or liqiuds, ΔV≅0. Therefore, 𝚫H=𝚫E.
Correct answer: 𝚫H=𝚫E- A. Thermo-chemistry
- B. Thermodynamics
- C. Electro chemistry
- D. Chemical kinetics
Explanation: Thermochemistry is the study of the heat energy which is associated with chemical reactions and/or phase changes such as melting and…
Correct answer: Thermo-chemistry718. Thermite process is:
- A. Exothermic
- B. Endothermic
- C. Reversible
- D. None of above
Explanation: Exothermic: An exothermic reaction is a chemical reaction that releases energy in the form of heat.
Correct answer: Exothermic- A. q = △E + W
- B. △E = q - W
- C. q = △E - P△V
- D. All of the above
Explanation: The first Law of Thermodynamics is represented by the formula: ΔE = q − W.
Correct answer: All of the above- A. First law of thermodynamics
- B. Henery's law
- C. Hess's law
- D. Joule's law
Explanation: Option A: The first law of thermodynamics states that energy can neither be created nor destroyed, only altered in form. Hence incorrect.
Correct answer: Hess's law