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# Thermochemical Calculations The document contains a series of thermochemical calculations, specifically enthalpy changes (ΔH) for various chemical reactions. The calculations use given data for standard enthalpy changes to determine the enthalpy change for a specific reaction based on the reacti...

# Thermochemical Calculations The document contains a series of thermochemical calculations, specifically enthalpy changes (ΔH) for various chemical reactions. The calculations use given data for standard enthalpy changes to determine the enthalpy change for a specific reaction based on the reactions provided. **Problem 81:** Calculate ΔH for the reaction: CaC₂(s) + 2H₂O(l) → Ca(OH)₂(aq) + C₂H₂(g) Given data: * Ca(s) + 2C(graphite) → CaC₂(s) ΔH = -62.8 kJ * Ca(s) + ½O₂(g) → CaO(s) ΔH = -635.5 kJ * CaO(s) + H₂O(l) → Ca(OH)₂(aq) ΔH = -653.1 kJ * C₂H₂(g) + 5/2O₂(g) → 2CO₂(g) + H₂O(l) ΔH = -1300. kJ * C(graphite) + O₂(g) → CO₂(g) ΔH = -393.5 kJ **Problem 82:** Calculate ΔH for the reactions: * P₄(s) + 6Cl₂(g) → 4PCl₃(g) ΔH = -1225.6 kJ * P₄(s) + 5O₂(g) → P₄O₁₀(s) ΔH = -2967.3 kJ * PCl₃(g) + Cl₂(g) → PCl₅(g) ΔH = -84.2 kJ **Note:** The table format is not clearly specified, but the text presents the reactions, reactants, products, and values of ΔH (enthalpy change). The format suggests the problems require finding the enthalpy change for a certain reaction based on the given enthalpy changes of other reactions. The compound formulas like `N₂O` are likely intended as reactants or products in equations (for instance, `N₂O(g)` is likely nitrogen monoxide gas). The unit for enthalpy changes is given as `kJ`. The abbreviations like `(g)`, `(l)`, `(s)`, and `(aq)` likely denote the physical states of the respective substances (gas, liquid, solid, aqueous solution).