Chemical energy is released or absorbed from reaction in various forms. The most

Question

Chemical energy is released or absorbed from reaction 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 where n represents the stoichiometric coefficients. calculate the standard enthalpy change for the reaction Use the following data: Express your answer to three significant figures and include the appropriate units. For the reaction given in part A, how much heat is absorbed when 2.70 mol of A reacts? Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

1 mole of A gives -265 KJ

1 mole of B gives -375 KJ

1 mole of C gives 219 KJ

1 mole of D gives -475 KJ

2A + B = 2C + 2D

2 mole of A + 1 mole of B = 2 mole of C + 2 mole of D

therefore,

2.7 mole of A + 1.35 of B = 2.7 mole of C + 2.7 mole of D

so the heat absorbed will be

{2.7x(219) + 2.7x(-475)} - {2.7x(-265) + 1.35x(-375)} = 530.55 KJ

the answer will be 530 KJ

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