Δ E must be zero for — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

Δ E (or Δ U) is a state function, so for any cyclic process Δ E = 0 (A correct). For an ideal gas, internal energy depends only on temperature, so for any isothermal process of an ideal gas Δ E = 0 (B correct). For a real gas, internal energy also depends on volume (due to intermolecular forces), so Δ E ≠ 0 during isothermal expansion (C incorrect). For an isothermal phase transition, heat of fusion is involved, so Δ E ≠ 0 (D incorrect).