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Ch.9 - Thermochemistry: Chemical Energy
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145당신이 사용하는 게 아니라요?교과서 변경
모든 교과서McMurry 8th EditionCh.9 - Thermochemistry: Chemical Energy문제 104
9장, 문제 104

Sulfuric acid (H2SO4), the most widely produced chemical in the world, is amde yb a two-step oxidaiton of sulfur to sulfur trioxide, SO3, followed by reaciton with water. Calculate ΔH°f for SO3 in kJ/mol, given the following data: S(s) + O2(g) → SO2(g) ΔH° = -296.8 kJ SO2(g) + 1/2 O2(g) → SO3(g) ΔH° = -98.9 kJ

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1
Identify the overall reaction for the formation of SO3 from its elements in their standard states. The overall reaction is: S(s) + 3/2 O2(g) → SO3(g).
Break down the overall reaction into the given steps and write down the enthalpy changes for each step. Step 1: S(s) + O2(g) → SO2(g), ΔH° = -296.8 kJ. Step 2: SO2(g) + 1/2 O2(g) → SO3(g), ΔH° = -98.9 kJ.
Add the enthalpy changes from the two steps to find the overall enthalpy change for the formation of SO3. Use the equation: ΔH°(overall) = ΔH°(step 1) + ΔH°(step 2).
Substitute the given values into the equation from step 3 to calculate the overall ΔH° for the formation of SO3.
The calculated ΔH° for the formation of SO3 from sulfur and oxygen is the ΔH°f (standard enthalpy of formation) of SO3.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Hess's Law

Hess's Law states that the total enthalpy change for a chemical reaction is the sum of the enthalpy changes for the individual steps of the reaction, regardless of the pathway taken. This principle allows us to calculate the enthalpy change for a reaction by using known enthalpy changes of related reactions, making it essential for determining ΔH°f values.
추천 영상:
가이드 코스
02:03
Hess's Law

Standard Enthalpy of Formation (ΔH°f)

The standard enthalpy of formation (ΔH°f) is defined as the change in enthalpy when one mole of a compound is formed from its elements in their standard states. It is a crucial concept in thermodynamics, as it provides a reference point for calculating the enthalpy changes of various reactions, including the formation of sulfur trioxide (SO3) in this case.
추천 영상:
가이드 코스
02:34
Enthalpy of Formation

Enthalpy Change (ΔH)

Enthalpy change (ΔH) refers to the heat content change of a system at constant pressure during a chemical reaction. It can be either exothermic (releasing heat, ΔH < 0) or endothermic (absorbing heat, ΔH > 0). Understanding how to manipulate ΔH values from given reactions is essential for calculating the enthalpy of formation for compounds like SO3.
추천 영상:
가이드 코스
02:34
Enthalpy of Formation
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The standard enthalpy change for the reaciton of SO3(g) with H2O(l) to yield H2SO4(aq) is ΔH° = -227.8 kJ. Use the information in Problem 9.104 to calculate ΔH°f for H2SO4(aq) in kJ/mol. [For H2O(l), ΔH°f = -285.88 kJ/mol.]
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