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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Brown 14th EditionCh.5 - Thermochemistry문제 74
5장, 문제 74

Using values from Appendix C, calculate the value of H for each of the following reactions: (a) CaO(s) + 2 HF(g) → CaF2(s) + H2O(g) (b) Fe2O3(s) + 3 C(s) → 2 Fe(s) + 3CO(g) (c) 2 CO(g) + 2 NO(g) → N2(s) + 2 CO2(g) (d) 4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2Og)

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1
Identify the standard enthalpy of formation (ΔH_f^°) for each compound involved in the reaction from Appendix C.
Write the balanced chemical equation: CaO(s) + 2 HF(g) → CaF_2(s) + H_2O(g).
Apply Hess's Law, which states that the change in enthalpy for a reaction is the sum of the enthalpy changes for each step of the reaction.
Calculate the enthalpy change (ΔH) for the reaction using the formula: ΔH = Σ(ΔH_f^° of products) - Σ(ΔH_f^° of reactants).
Substitute the values of ΔH_f^° for each compound into the formula and perform the arithmetic to find the enthalpy change for the reaction.

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주요 개념

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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). Calculating ΔH for a reaction often involves using standard enthalpy values from tables, which represent the enthalpy of formation for various substances.
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가이드 코스
02:34
Enthalpy of Formation

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is the same, regardless of the number of steps taken to achieve the reaction. This principle allows chemists to calculate the enthalpy change for complex reactions by summing the enthalpy changes of individual steps, making it easier to find ΔH using tabulated values.
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가이드 코스
02:03
Hess's Law

Standard Enthalpy of Formation

The standard enthalpy of formation (ΔH°f) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. These values are crucial for calculating the enthalpy change of a reaction using the formula ΔH = ΣΔH°f(products) - ΣΔH°f(reactants), allowing for the determination of the overall energy change during a chemical reaction.
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가이드 코스
02:34
Enthalpy of Formation
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