Chemical Thermodynamics

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A thermodynamic system is the part of the universe under study for energy changes. It is separated from the surroundings by boundaries. Example: Hot coffee in a cup - the coffee is the system, while t…

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Open system: Exchanges both energy and matter (hot coffee in open cup). Closed system: Exchanges only energy, not matter (coffee in covered cup). Isolated system: No exchange of energy or matter (coff…

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State functions are properties that depend only on the state of the system, not the path taken to reach that state. Examples: Pressure (P), Volume (V), Temperature (T), Internal Energy (U), Enthalpy (…

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W = -Pₑₓₜ ΔV = -Pₑₓₜ(V₂ - V₁) Sign convention: +W: Work done ON the system (compression) -W: Work done BY the system (expansion) For expansion: V₂ > V₁, so W is negative For compression: V₂ < V₁, so…

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First Law of Thermodynamics: Energy can neither be created nor destroyed, only converted from one form to another. The total energy of the universe remains constant. Mathematical expression: ΔU = Q +…

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Enthalpy (H) is the sum of internal energy and pressure-volume work: H = U + PV Derivation: ΔH = H₂ - H₁ = (U₂ + P₂V₂) - (U₁ + P₁V₁) ΔH = ΔU + Δ(PV) At constant pressure: P₁ = P₂ = P ΔH = ΔU + PΔV E…

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Starting from ΔH = ΔU + PΔV For ideal gases: PV = nRT For reactants: PV₁ = n₁RT For products: PV₂ = n₂RT Therefore: PΔV = P(V₂ - V₁) = PV₂ - PV₁ = n₂RT - n₁RT = (n₂ - n₁)RT ΔH = ΔU + ΔnₘRT where Δnₘ…

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Standard enthalpy of formation (Δf H°) is the enthalpy change when 1 mole of a compound is formed from its constituent elements in their standard states at 1 bar pressure and 298 K. H₂(g) + ½O₂(g) → …