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 19 of 37
- A. 5/3
- B. 1.3
- C. 4/3
- D. 7/5
Explanation: The heat capacity ratio of a gas is the ratio Cp and Cv. γ = Cp/Cv
Correct answer: 5/3- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Standard enthalpy of atomization is the enthalpy change that occurs when one mole of a sample is dissociated into its atoms under standard…
Correct answer: Option C- A. Exothermic reactions
- B. Decomposition reactions
- C. Dissociation reaction
- D. Endothermic reactions
Explanation: In exothermic reactions, heat is released to the surroundings as a product.
Correct answer: Exothermic reactions- A. Remains unchanged
- B. Increases
- C. Increases than decreases
- D. Decreases
Explanation: The enthalpy of atomization is the enthalpy change that accompanies the total separation of all atoms in a chemical substance.
Correct answer: Decreases365. What will be the enthalpy change in the reaction given below?2H2 + O2→ 2H2O ∆H = +205.5 kJ mol-1
- A. 205.5 kJ/mol
- B. Zero kJ/mol
- C. -205.5 kJ/mol
- D. 1 kJ/mol
Explanation: This is a trick question. Most students choose A however that is wrong.
Correct answer: -205.5 kJ/mol- A. -394 kJ/mol
- B. +394 kJ/mol
- C. -294 kJ/mol
- D. -390 kJ/mol
Explanation: The heat of formation (∆Hf°) for carbon dioxide (CO2) is: ∆Hf° = -394 kj/molThe negative sign indicates that the formation of one moleucle…
Correct answer: -394 kJ/mol- A. Exothermic reactions
- B. Endothermic reactions
- C. Photochemical reactions
- D. Non-spontaneous reactions
Explanation: In exothermic reactions, the energy of the reactants is higher than that of the products.
Correct answer: Exothermic reactions- A. Heat is evolved
- B. Heat is absorbed
- C. Heat may be evolved or absorbed
- D. Electrolyte does not dissolve in water
Explanation: A solution is a homogeneous mixture of two or more substances and can either be in the gas phase, the liquid phase, or the solid phase.
Correct answer: Heat may be evolved or absorbed- A. Increase in boiling point of liquid and decrease in melting point of solid
- B. Increase in both boiling and melting points
- C. Decrease in boiling point of liquid and increase in melting point of solid
- D. Decrease in both boiling and melting points
Explanation: Whenever a soluble, non-volatile impurity is added to a liquid, some of the solute particles tend to migrate toward the surface of the…
Correct answer: Increase in boiling point of liquid and decrease in melting point of solid- A. China dish
- B. Burner
- C. Laboratory
- D. 𝐶𝑎𝐶𝑂3
Explanation: The system is the collective substances in the reaction such as the reactants and products.
Correct answer: 𝐶𝑎𝐶𝑂3- A. Dissolution
- B. Crystallization
- C. Bond breaking
- D. Condensation
Explanation: The process of dissolving can be endothermic (temperature goes down) or exothermic (temperature goes up).
Correct answer: Dissolution- A. 436Kj/mol
- B. 40.7 Kj/mol
- C. 272 Kj/mol
- D. 436÷Avagadros no Kj/mol
Explanation: Bond energy is the amount of energy required to break one mole of covalent bonds in a gaseous molecule, resulting in separate gaseous…
Correct answer: 436Kj/mol- A. CaCl2
- B. K2O
- C. CaO
- D. BaCl2
Explanation: CaO has higher lattice energy because the lattice energy increases when the charge on the atom increases.
Correct answer: CaO- A. △H= qw
- B. △E=q - P△V
- C. △H=q+w
- D. △E = q+W
Explanation: The first law of thermodynamics states that the change in internal energy (△E) of a system is equal to the heat (q) added to the system…
Correct answer: △E=q - P△V- A. Activation energy
- B. Ionization energy
- C. Bond Energy
- D. Potential energy
Explanation: Bond energy is the amount of energy required to break one mole of a particular type of bond in a molecule or compound.
Correct answer: Bond Energy- A. △H = 213 kcal/mole
- B. △H = 231 kcal/mole
- C. △H = 426 kcal/mole
- D. △H = 312 kcal/mole
Explanation: The enthalpy of combustion of methane (CH4) is -890 kJ/mol. To convert this to kilocalories, use the conversion factor 1 kJ = 0.239 kcal.
Correct answer: △H = 213 kcal/mole- A. ∆E=q+W
- B. ∆E=-q+W
- C. ∆E=-q-W
- D. ∆E=q-W
Explanation: The expression for 1st law of thermodynamics is ΔE = q-w STB Pg- 157
Correct answer: ∆E=q+W- A. ∆E - P∆V
- B. ∆E + P∆V
- C. -∆E + P∆V
- D. -∆E - P∆V
Explanation: ΔH is known as change in enthalpy which is the sum of internal energy and work done. Hence, ΔH = ΔE + PΔVSo, option B is correct.
Correct answer: ∆E + P∆V- A. Low temperature
- B. High pressure
- C. Continuous removal of NH3
- D. Continuous addition of NH3
Explanation: In the Haber's process, ammonia is synthesized from nitrogen and hydrogen gases.
Correct answer: Continuous addition of NH3- A. Zero
- B. Positive
- C. Negative
- D. Constant
Explanation: In an exothermic reaction, heat is released, so the enthalpy change (ΔH°) is negative.
Correct answer: Negative