During isothermal expansion of an ideal gas, its

Question

During isothermal expansion of an ideal gas, its (A) internal energy increases (B) enthalpy increases (C) enthalpy reduces to zero (D) enthalpy remains unchanged.

Tardigrade Admin · Accepted Answer

An isothermal process is a change of a system, in which the temperature remains constant. For an ideal gas during an isothermal expansion the enthalpy, as well as internal energy, remains constant.

During isothermal expansion of an ideal gas,

Δ E = 0, Δ T = 0

From the definition of enthalpy,

H = E + P V

or

Δ H = Δ E + Δ (P V)

or

Δ H = Δ E + Δ (n RT)

Since, PV=nRT for an ideal gas

or

Δ H = Δ E + n R Δ T

or

Δ H = 0

Q. During isothermal expansion of an ideal gas, its

internal energy increases

enthalpy increases

enthalpy reduces to zero

enthalpy remains unchanged.