NEET Chemistry: Chemical Thermodynamics Practice Questions

Correct answer: C — The system released energy to the surroundings.

Work done *by* the system (W) is negative when the system expands against an external pressure (work is done *on* the system). If the question refers to the work done *by* the system being negative, it implies that the system has released energy to the surroundings (if considering the energy flow into the system), or the net change in internal energy calculation reflects energy leaving the system if we use ΔU = Q - W.

Correct answer: C — Intensive

Density is defined as mass per unit volume. Since it is independent of the amount of substance, it is an intensive property.

Correct answer: B — ΔU = Q - W

For an isolated system, the First Law of Thermodynamics states that the change in internal energy is equal to the heat supplied to the system minus the work done by the system (ΔU = Q - W).

Correct answer: C — The surroundings can exchange energy and matter with the system.

The surroundings are the environment outside the system, and thermodynamic processes inherently involve the exchange of energy or matter between the system and its surroundings.

Correct answer: C — Adiabatic process

An adiabatic process is a thermodynamic process in which no heat is exchanged with the surroundings.

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: D — Heat and work are both path functions.

Heat (Q) and work (W) are path functions, meaning their values depend on the specific path taken between the initial and final states, whereas internal energy (ΔU) is a state function.

Correct answer: B — Isochoric process

An isochoric process is defined as a process where the volume of the system remains constant (V = constant).

Correct answer: A — +10 kJ

By summing the two reactions, X → Y and Y → Z, we get X → Z. ΔHₒᵥₑᵣₐₗₗ = ΔH₁ + ΔH₂ = (-20 kJ) + (+30 kJ) = +10 kJ.

Correct answer: D — Cₚ - Cᵥ = R

For any ideal gas, the relationship between molar heat capacity at constant pressure (Cₚ) and molar heat capacity at constant volume (Cᵥ) is given by Mayer's relation: Cₚ - Cᵥ = R, where R is the universal gas constant.

Correct answer: C — No energy exchange

An isolated system cannot exchange energy with its surroundings. Therefore, for an isolated system, ΔU = Q + W = 0 (if no boundary work is considered, or more accurately, changes are balanced internally).

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 — Change in Enthalpy (ΔH)

When the process occurs at constant pressure, the heat exchanged is equal to the change in enthalpy (ΔH), which is defined as Qₚ = ΔH for pressure-volume work calculations.