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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 15th Edition
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Tutti i libri di testoBrown 15th EditionCh.5 - ThermochemistryProblema 40b
Capitolo 5, Problema 40b

The decomposition of Ca(OH)2 into CaO(s) and H2O at constant pressure requires the addition of 109 kJ of heat per mole of Ca(OH)2 . b. Draw an enthalpy diagram for the reaction.

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Draw a horizontal line to represent the enthalpy level of the reactants, Ca(OH)_2.
Since the reaction is endothermic, draw an upward arrow from the reactants' line to indicate the absorption of heat.
Label the upward arrow with the amount of heat absorbed, 109 kJ/mol.
Draw another horizontal line above the reactants' line to represent the enthalpy level of the products, CaO and H_2O.
Label the products' line with the chemical formulas of the products, CaO(s) and H_2O(g).

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Enthalpy (ΔH)

Enthalpy is a thermodynamic property that represents the total heat content of a system at constant pressure. It is defined as the sum of the internal energy and the product of pressure and volume. In chemical reactions, the change in enthalpy (ΔH) indicates whether a reaction is exothermic (releases heat) or endothermic (absorbs heat), which is crucial for understanding the energy changes during the decomposition of Ca(OH)₂.
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Decomposition Reaction

A decomposition reaction is a type of chemical reaction where a single compound breaks down into two or more simpler products. In this case, calcium hydroxide (Ca(OH)₂) decomposes into calcium oxide (CaO) and water (H₂O). Understanding the nature of decomposition reactions helps in predicting the products and the energy changes involved, such as the heat required for the reaction to proceed.
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Enthalpy Diagram

An enthalpy diagram, or reaction coordinate diagram, visually represents the energy changes during a chemical reaction. It typically shows the enthalpy of the reactants and products, along with the activation energy and the overall change in enthalpy (ΔH). For the decomposition of Ca(OH)₂, the diagram would illustrate the energy input required (109 kJ) to break the bonds in the reactant, leading to the formation of products at a higher energy level.
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