Question

Chemical energy is released or absorbed from reactions in various forms. The most easily measurable form of energy comes in the form of heat, or enthalpy. The enthalpy of a reaction can be calculated from the heats of formation of the substances involved in the reaction:

ΔH∘rxn=ΔH∘f(products)−ΔH∘f(reactants)

Entropy change, ΔS∘, is a measure of the number of energetically equivalent microstates introduced into the system during the reaction. The degree of spontaneity of a reaction is represented by the Gibbs free energy, ΔG∘. The Gibbs free energy depends on both the enthalpy and entropy changes that take place during the reaction:

ΔG∘=ΔH∘−TΔS∘

where T is standard temperature, 298 K.

Part A Calculate the standard enthalpy change for the reaction 2A+B⇌2C+2D where the heats of formation are given in the following table: Substance ΔH∘f (kJ/mol) A -241 B -397 C 209 D -477 Express your answer in kilojoule

Answer 1

Pant A Stondand chhatpy Anthe reaction 2A+ 8 20+2D Con be calulate by ДИ 9УИ. -2 AHr () t 2x 4HE (D) LAHECA)X2 + AH CB) ДИлn 2x 209 t 2x(-477) 2 L(2x-241 241 AHnh 127 KJ C this nh is atethernic in nature