Skip to main content
Ch.9 - Thermochemistry: Chemical Energy
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoMcMurry 8th EditionCh.9 - Thermochemistry: Chemical EnergyProblema 143a
Capitolo 9, Problema 143a

Methanol (CH3OH) is made industrially in two steps from CO and H2. It is so cheap to make that it is being considered for use as a precursor to hydrocarbon fuels, such as methane (CH4):
Step 1. CO(g) + 2 H2(g) → CH3OH(l) ΔS° = –332 J/K
Step 2. CH3OH(l) → CH4(g) + 1/2 O2(g) ΔS° = 162 J/K
(a) Calculate ΔH° in kilojoules for step 1.

Guida verificata passo dopo passo
1
Identify the given values and the required calculation. For step 1, you are given the standard entropy change (ΔS°) and need to calculate the standard enthalpy change (ΔH°).
Recall the Gibbs free energy equation: ΔG° = ΔH° - TΔS°. You will need to rearrange this equation to solve for ΔH°.
Since the problem does not provide the temperature (T) or the Gibbs free energy change (ΔG°), you need to assume standard conditions. Standard temperature is typically 298 K.
Rearrange the Gibbs free energy equation to solve for ΔH°: ΔH° = ΔG° + TΔS°.
To find ΔG°, use the standard relation at equilibrium where ΔG° = 0. Substitute this value and the given ΔS° into the rearranged equation to calculate ΔH°.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
3m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

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). To calculate ΔH°, one typically uses the standard enthalpies of formation of the reactants and products involved in the reaction.
Video consigliato:
Percorso guidato
02:34
Enthalpy of Formation

Gibbs Free Energy and Entropy (ΔS°)

Gibbs free energy (G) combines enthalpy and entropy to predict the spontaneity of a reaction. The change in entropy (ΔS°) reflects the disorder of a system; a negative ΔS° indicates a decrease in disorder, while a positive ΔS° indicates an increase. Understanding the relationship between ΔH°, ΔS°, and temperature is crucial for determining the feasibility of a reaction.
Video consigliato:
Percorso guidato
01:51
Gibbs Free Energy of Reactions

Stoichiometry in Chemical Reactions

Stoichiometry involves the calculation of reactants and products in chemical reactions based on balanced equations. It allows chemists to predict the amounts of substances consumed and produced. In the context of the given question, stoichiometry is essential for determining the moles of CO and H2 required to produce methanol, which directly influences the calculation of ΔH° for the reaction.
Video consigliato:
Percorso guidato
01:16
Stoichiometry Concept
Pratica correlata
Domanda del libro di testo

What is the melting point of benzene in kelvin if ΔHfusion = 9.95 kJ/mol and ΔSfusion = 35.7 J/(K mol)?

485
views
Domanda del libro di testo

Methanol (CH3OH) is made industrially in two steps from CO and H2. It is so cheap to make that it is being considered for use as a precursor to hydrocarbon fuels, such as methane (CH4):

Step 1. CO(g) + 2 H2(g) → CH3OH(l) ΔS° = –332 J/K

Step 2. CH3OH(l) → CH4(g) + 1/2 O2(g) ΔS° = 162 J/K

(f) Calculate ΔH° for step 2.

369
views
Domanda del libro di testo
Metallic mercury is obtained by heating the mineral cinnabar (HgS) in air: HgS1s2 + O21g2 S Hg1l2 + SO21g2 (a) Use the data in Appendix B to calculate ΔH° in kilojoules for the reaction.
720
views
Domanda del libro di testo
Ethyl chloride 1C2H5Cl2, a substance used as a topical anes-thetic, is prepared by reaction of ethylene with hydrogen chloride: C2H41g2 + HCl1g2 ¡ C2H5Cl1g2 ΔH° = - 72.3 kJ How much PV work is done in kilojoules, and what is the value of ΔE in kilojoules if 89.5 g of ethylene and 125 g of HCl are allowed to react at atmospheric pressure and the volume change is - 71.5 L?
904
views
Domanda del libro di testo

Methanol (CH3OH) is made industrially in two steps from CO and H2. It is so cheap to make that it is being considered for use as a precursor to hydrocarbon fuels, such as methane (CH4):

Step 1. CO(g) + 2 H2(g) S CH3OH(l) ΔS° = - 332 J/K

Step 2. CH3OH(l) → CH4(g) + 1/2 O2(g) ΔS° = 162 J/K

(e) In what temperature range is step 1 spontaneous?

391
views