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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 15th EditionCh.5 - ThermochemistryProblema 46a
Capitolo 5, Problema 46a

At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO3: 2 KClO3(s) → 2 KCl(s) + 3 O2(g) ΔH = -89.4 kJ For this reaction, calculate H for the formation of (a) 1.36 mol of O2

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Identify the given reaction: 2 KClO_3(s) → 2 KCl(s) + 3 O_2(g) with ΔH = -89.4 kJ.
Understand that ΔH = -89.4 kJ is for the formation of 3 moles of O_2.
Set up a proportion to find ΔH for 1.36 moles of O_2: (ΔH for 1.36 mol O_2) / (ΔH for 3 mol O_2) = 1.36 mol / 3 mol.
Solve the proportion to find ΔH for 1.36 moles of O_2.
Ensure the units are consistent and the sign of ΔH reflects the exothermic nature of the reaction.

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Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows us to calculate the amounts of substances consumed and produced in a reaction based on balanced chemical equations. In this case, the stoichiometric coefficients from the reaction indicate that 3 moles of O2 are produced for every 2 moles of KClO3 decomposed.
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Stoichiometry Concept

Enthalpy Change (ΔH)

Enthalpy change (ΔH) is a measure of the heat content of a system at constant pressure. It indicates whether a reaction is exothermic (releases heat, ΔH < 0) or endothermic (absorbs heat, ΔH > 0). In the given reaction, ΔH = -89.4 kJ signifies that the decomposition of KClO3 releases 89.4 kJ of energy for every 2 moles of KClO3 reacted, which is crucial for calculating the energy change for the formation of 1.36 moles of O2.
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Enthalpy of Formation

Molar Relationships

Molar relationships refer to the ratios of moles of reactants and products in a balanced chemical equation. These relationships are essential for converting between moles of different substances. In this scenario, knowing that 3 moles of O2 are produced from 2 moles of KClO3 allows us to determine the amount of energy associated with the formation of 1.36 moles of O2 by using the established stoichiometric ratios.
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Molarity
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