Thermodynamics

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A thermodynamic system is that part of the universe in which observations are made. The remaining universe constitutes the surroundings. Example: If we study a reaction between substances A and B in a

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Open system: Exchange of both matter and energy with surroundings (e.g., reactants in an open beaker). Closed system: Exchange of energy only, no matter exchange (e.g., reactants in a sealed steel con

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State functions are properties whose values depend only on the state of the system, not on how that state was reached. Examples: Internal energy (U), enthalpy (H), pressure (p), volume (V), temperatur

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The First Law of Thermodynamics states that energy can neither be created nor destroyed, only converted from one form to another. Mathematical expression: ΔU = q + w, where ΔU is change in internal en

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For a reversible process at constant temperature: w = -∫PdV. For an ideal gas, P = nRT/V, so w = -∫(nRT/V)dV = -nRT∫(dV/V) = -nRT ln(Vf/Vi) = -2.303 nRT log(Vf/Vi). The negative sign indicates work do

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Enthalpy (H) = U + pV. At constant pressure, ΔH = qp (heat absorbed at constant pressure). Since most chemical reactions occur at constant atmospheric pressure, enthalpy change directly measures the h

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ΔH = ΔU + ΔngRT, where Δng = (moles of gaseous products) - (moles of gaseous reactants). For reactions involving only solids and liquids, ΔH ≈ ΔU since volume changes are negligible. For gas reactions

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Standard enthalpy of formation is the enthalpy change when one mole of a compound is formed from its constituent elements in their most stable states at 1 bar pressure and 298 K. By convention, ΔfH⊖ =