Free Enthalpy MCQs with Answers

• A. internal energy
• B. enthalpy
• C. entropy
• D. free energy

Explanation: Enthalpy was defined precisely so that its change measures the heat of a process at constant pressure, which is the condition of almost…

• A. always negative
• B. always positive
• C. zero by definition
• D. equal to its atomic mass

Explanation: Forming an element from itself involves no change, so the value is defined as zero and this provides the reference point from which all…

• A. one mole of a substance is burnt completely in excess oxygen under standard conditions
• B. one gram of a substance is burnt
• C. one mole of a substance is formed from its elements
• D. one mole of a substance is dissolved in water

Explanation: The definition specifies one mole, complete combustion and excess oxygen, and combustion values are always negative because burning…

• A. Heat of transition
• B. Heat of fusion
• C. Enthalpy change
• D. All of above

Explanation: At constant pressure, the heat absorbed or released by a process is equal to its enthalpy change, q_p = delta H.

• A. Negative
• B. Positive
• C. May or may not be A or B
• D. none

Explanation: An enthalpy change is the heat change at constant pressure, so it may be positive for an endothermic process or negative for an exothermic…

• A. 0 atmosphere
• B. one atmosphere
• C. 2 atmosphere
• D. 10 atmosphere

Explanation: Molar heat of fusion is conventionally measured at constant atmospheric pressure, so the pressure is 1 atmosphere.

• A. glass calorimeter
• B. bomb calorimeter
• C. thermometer
• D. manometer

Explanation: A bomb calorimeter measures heat released by burning a substance in a sealed vessel at constant volume, allowing accurate measurement of…

• A. glass calorimeter
• B. manometer
• C. Barometer
• D. thermometer

Explanation: A calorimeter measures the heat absorbed or released by a reaction, and at constant pressure this heat is related to the reaction…

• A. Hydrazine
• B. Both have equal enthalpy of formation
• C. Hydrogen gas
• D. Cannot be compared

Explanation: The performance of rocket fuel is measured by its enthalpy of combustion, which is the amount of heat released when one mole of the fuel…

• A. Enthalpy
• B. Surrounding
• C. Work
• D. Internal energy

Explanation: internal energy is equal to enhalpy change and work doneH=E+PV

• A. Delta*H_{v} > Delta*H_{f}
• B. Delta*H_{s} > Delta*H_{f}
• C. Delta*H_{f} > Delta*H_{r}
• D. Delta*H_{x} > Delta*H_{v}

Explanation: deltaHf is less than deltaHr because in formation only specific product with one mole forms but in reaction all type of reaction are…

• A. Evolved
• B. Absorbed
• C. Either Evolved or Absorbed
• D. None of the above

Explanation: The heat of formation, also known as the standard enthalpy of formation, is the heat change accompanying the formation of one mole of a…

• A. Heat of formation of one mole of salt
• B. Heat of formation of one mole of water
• C. Both a and b
• D. None of these

Explanation: The heat of neutralization is defined as the heat change that occurs when one mole of water is formed by the combination of an acid and a…

• A. Change in internal energy (ΔE)
• B. Change in enthalpy (ΔH)
• C. Change in free energy (ΔG)
• D. Change ín temperature only (ΔT)
• E. Change in pressure only (ΔP)

Explanation: At constant pressure, the heat of reaction is equal to the enthalpy change of the system.

• A. 3.426 kJ
• B. 13.7 kJ
• C. 5.2 kJ
• D. 55 kJ

Explanation: The balanced chemical equation for the neutralization is: H2SO4(aq) + 2KOH(aq) → K2SO4(aq) + 2H2O(l).

• A. 379 kJ
• B. 215 kJ
• C. 208 kJ
• D. 315 kJ

Explanation: First, convert the mass of CO₂ to moles: 35.2 g / 44 g/mol = 0.8 mol. The heat released is then the number of moles multiplied by the…

• A. 100 gm
• B. 180 gm
• C. 200 gm
• D. 120 gm

Explanation: Work(W) = m * g * h Where: m = mass of the person = 100kg g = acceleration due to gravity = 10 m/s^2 h = height of the hill = 500meters W…

• A. 1238.78 J mol−1
• B. −2477.57 J mol−1
• C. 2477.57 J mol−1
• D. −1238.78 J mol−1

Explanation: C(s) + ½O(g) → CO(g) ∆H = ∆U + ∆ngRT (∆H − ∆U) = ∆ngRT= 1/2 x 8.314 x 298 = −1238.78 J mol−1

• A. endothermic
• B. exothermic
• C. ∆H = 0
• D. none of the above

Explanation: ∆H = (∆Hf°)Products - (∆Hf°)Reactants = 3 × (- 393.7) - 2 × (-824.2) = 476.3 kJ/mole (remember the formula for further use)

• A. 20 ml acid and 30 ml alkali
• B. 10 ml acid and 40 ml alkali
• C. 25 ml acid and 25 ml alkali
• D. 35 ml acid and 15 ml alkali

Explanation: When 25 ml acid reacts with 25 ml of alkali, maximum equivalent of acid is reacting with alkali.