NEET Chemistry: Enthalpy Practice Questions

Correct answer: D — Enthalpy (H)

State functions are properties of a system that depend only on the initial and final states, not on the path taken between them. Enthalpy (H) is a state function, while heat (Q) is a path function.

Correct answer: C — Enthalpy (H)

Enthalpy (H) is a state function. It depends only on the thermodynamic state of the system (pressure, volume, and temperature), making it independent of the process path. Heat (q) is a path function, while Internal Energy (U) is also a state function, but Enthalpy is the specific thermodynamic potential often associated with constant pressure processes.

Correct answer: D — The heat absorbed or released by the system.

Enthalpy change (ΔH) is precisely the heat absorbed or released by the system during the process when the pressure is constant.

Correct answer: C — State function

Enthalpy is a state function, meaning its value depends only on the initial and final states of the system, not the path taken between them.

Correct answer: B — ΔH is the heat absorbed or released at constant pressure.

Enthalpy change (ΔH) is the heat absorbed or released by the system at constant pressure. It is a state function, meaning the change depends only on the initial and final states, not the path taken.

Correct answer: B — Conservation of Energy

The First Law of Thermodynamics states that energy cannot be created or destroyed; it is conserved. This principle forms the basis for all enthalpy calculations.

Correct answer: B — State function

Enthalpy (H) is a state function, meaning its value depends only on the initial and final states of the system, not on the process taken to reach those states.

Correct answer: D — Enthalpy (H)

A state function is a property that depends only on the current state of the system, not the path taken. Enthalpy (H) is a state function, whereas heat (q) and work (w) are path functions.

Correct answer: B — The heat absorbed when one mole of the element is formed from its elements in their standard states.

The standard enthalpy of formation (ΔH_f°) is the enthalpy change when one mole of a compound is formed from its constituent elements in their respective standard states.

Correct answer: A — Exothermic

A negative enthalpy change (ΔH < 0) indicates that the system releases energy to the surroundings, which defines an exothermic process. An endothermic reaction has a positive ΔH.

Correct answer: B — Kilojoules per mole (kJ/mol)

Enthalpy is a form of energy. The standard SI unit for energy is the Joule (J). For enthalpy change, the standard unit is kilojoules per mole (kJ/mol) or joules per mole (J/mol).

Correct answer: C — Heat (Q)

Heat (Q) is a path function, meaning its value depends on the process taken between two states, whereas Enthalpy (H), Internal Energy (U), and Gibbs Free Energy (G) are state functions.

Correct answer: B — Heat exchanged at constant pressure

Enthalpy (H) is defined as H = U + PV. Therefore, the change in enthalpy (ΔH) is equal to the heat exchanged (qₚ) under constant pressure.

Correct answer: C — First Law of Thermodynamics

Hess's Law states that the total enthalpy change for a chemical reaction is the same regardless of the path taken, which is a direct consequence of the First Law of Thermodynamics (conservation of energy).

Correct answer: D — ΔH represents the total heat exchanged with the surroundings during the reaction.

Enthalpy change (ΔH) is the heat exchanged during a process at constant pressure. In a closed system, it represents the heat absorbed or released by the system due to the reaction. Options A and C are incomplete or incorrect definitions. Option B captures the essence of enthalpy as the heat interaction with the surroundings (the environment).