Standard State & Enthalpy Explained in 1 Minute! ⚡ | JEE Main Chemistry Concept
❓ Question Which of the following statements is correct ? 1️⃣ Δ f H 298 ∘ \Delta_f H^\circ_{298} Δ f H 298 ∘ is zero for O(g) 2️⃣ The standard state of a pure gas is the pure gas at a pressure of 1 bar and temperature 273 K 3️⃣ The term standard state implies that the temperature is 0 °C 4️⃣ Δ f H 500 ∘ \Delta_f H^\circ_{500} Δ f H 500 ∘ is zero for O₂(g) 🖼️ Question Image ✍️ Short Solution Let’s analyze each statement carefully using thermodynamic definitions. 🔹 Step 1 — Recall definition of standard enthalpy of formation (ΔfH°) The standard enthalpy of formation is the enthalpy change when 1 mol of a substance is formed from its constituent elements in their most stable states at 1 bar pressure and a specified temperature (usually 298 K ). By convention: Δ f H ∘ = 0 for all elements in their standard states at 298 K. 🔹 Step 2 — Check each statement (1) Δ f H 298 ∘ \Delta_f H^\circ_{298} is zero fo...