Free Thermochemistry and Energetics of Chemical Reactions MCQs with Answers

• A. can be measured by calorimeter
• B. calculated by Hess's law
• C. none
• D. both a and b

Explanation: Explanation: Enthalpy change can be measured by a calorimeter and calculated using Hess's law.

• A. Heat
• B. Pressure
• C. Volume
• D. Enthalpy

Explanation: A state function is a property whose value depends only on the current state of a system, not on the path taken to reach that state.

• A. The first law of thermodynamics is not sufficient to predict the direction of a process
• B. In the case of an exothermic reaction, the overall enthalpy of the products is greater than that of the reactants
• C. For the reaction H₂(g) + Br₂(l) → 2HBr(g), the enthalpy change can be calculated from bond enthalpy data alone
• D. At 298K and 1 atm pressure, diamond's standard enthalpy of formation is zero

Explanation: The first law deals with the conservation of energy but provides no information about the direction in which a process will spontaneously…

• A. ΔH is positive for an exothermic reaction
• B. ΔH is negative for an endothermic reaction
• C. The heat of neutralization of a strong acid with a strong base is always the same
• D. The enthalpy of fusion is negative

Explanation: The neutralization of any strong acid with any strong base always involves the same net ionic reaction: H⁺(aq) + OH⁻(aq) → H₂O(l).

• A. C(s) + O₂(g) → CO₂(g)
• B. 2H₂(g) + O₂(g) → 2H₂O(l)
• C. N₂(g) + O₂(g) → 2NO(g)
• D. CaO(s) + H₂O(l) → Ca(OH)₂(aq)

Explanation: The formation of nitric oxide (NO) from nitrogen and oxygen is a highly endothermic reaction, meaning it requires a significant input of…

• A. ΔH is positive for endothermic reactions.
• B. ΔH is negative for exothermic reactions.
• C. In the equation ΔE = q - PΔV, where q = ΔV.
• D. All the above are correct.

Explanation: Option C is the correct answer because it contains an incorrect statement.

• A. Exothermic
• B. Spontaneous
• C. Non-Spontaneous
• D. None of these

Explanation: It is a spontaneous process as entropy increases with the change in state.

• A. Al2O3
• B. B2O3
• C. CCL4
• D. All of these options are correct

Explanation: Frankly speaking, We don't know the absolute enthalpy of a substance because we don't know where absolute Zero is.

• A. Rotational & vibrational
• B. Translation & rotational
• C. Rotational, vibrational and translatio
• D. All of these

Explanation: Kinetic energy is the sum of translational, rotational, and vibrational kinetic energies, representing the various forms of motion…

• A. Internal Energy
• B. Enthalpy
• C. Work
• D. None of these options are correct

Explanation: Option C is correct since work can not be a state function as it is proportional to the distance an object is moved.

• A. Total energy of the system and surrounding is conserved
• B. Energy can neither be created nor destroyed
• C. It is the same as law of conservation of energy
• D. Total energy of the system is increasing

Explanation: The total energy of the system remains constant. Hence, statement D is not correct.

• A. decreasing the activation energy
• B. decreasing the concentration of reactants
• C. decreasing the temperature
• D. increasing the temperature

Explanation: A catalyst increases the rate of reaction in both forward and backward directions by providing an alternate pathway with lower activation…

• A. Total heat
• B. Work done
• C. Entropy
• D. Internal energy

Explanation: For an isochoric process, the volume remains constant. Since; Work done = PΔV, for constant volume, ΔV= 0,, hence work done has a constant…

• A. Al2O3
• B. B2O3
• C. CO
• D. All of these options are correct

Explanation: Frankly speaking, We don't know the absolute enthalpy of a substance because we don't know where absolute Zero is.

• A. Spontaneous reaction
• B. Exothermic Reaction
• C. Reversible Reaction
• D. Combustion Reaction

Explanation: OPTION A: Because ∆G =∆H - T∆S at this temperature ∆G = 0, indicating that the liquid and vapor phases are in equilibrium.

• A. Rotational & Vibrational
• B. Translation & Rotational
• C. Rotational, Vibrational, and Translation
• D. All of these

Explanation: The kinetic energy of an object with translational and rotational motion is the sum of its translational and its rotational kinetic…

• A. Exothermic reaction
• B. Endothermic reaction
• C. Spontaneous reaction
• D. Nonspontaneous reaction

Explanation: The term exothermic process describes a process or reaction that releases energy from the system to its surroundings, usually in the form…

• A. q=m s ∆T
• B. E=q m ∆T
• C. E=m s ∆T
• D. E=m c ∆T

Explanation: Q=ms ∆T is the equation of specific heat. Each term in the equation has a different significance.

• A. -394 kJ/mole
• B. +394 kJ/mole
• C. -294 kJ/mole
• D. -390 kJ/mole

Explanation: The heat of formation (∆Hf°) for carbon dioxide (CO2) is: ∆Hf° = -394 kj/mol The negative sign indicates that the formation of one…

• A. Heat is evolved
• B. Heat is absorbed
• C. Heat may evolved or absorbed
• D. Electrolyte do 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.