Skip to main content
Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.5 - ThermochemistryProblema 47d
Capitolo 5, Problema 47d

Consider the combustion of liquid methanol, CH3OH(l): CH3OH(l) + 3/2 O2(g) → CO2(g) + 2 H2O(l) ΔH = -726.5 kJ (d) If the reaction were written to produce H2O(g) instead of H2O(l), would you expect the magnitude of ΔH to increase, decrease, or stay the same? Explain.

Guida verificata passo dopo passo
1
Understand that the enthalpy change (ΔH) given is for the formation of liquid water (H2O(l)) from the combustion of methanol.
Recall that converting liquid water to gaseous water (H2O(g)) requires additional energy, known as the enthalpy of vaporization.
Recognize that if the reaction produces H2O(g) instead of H2O(l), the system must supply this additional energy to vaporize the water.
Since energy is required to convert H2O(l) to H2O(g), the magnitude of ΔH for the reaction will increase (become less negative) because the system absorbs more energy.
Conclude that the enthalpy change for the reaction producing H2O(g) will be less exothermic compared to the reaction producing H2O(l), due to the added energy requirement for vaporization.

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:
2m

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 absorbed or released during a chemical reaction at constant pressure. In exothermic reactions, like the combustion of methanol, ΔH is negative, indicating that heat is released. The magnitude of ΔH reflects the energy difference between reactants and products, which can vary depending on the physical states of the products formed.
Video consigliato:
Percorso guidato
02:34
Enthalpy of Formation

Phase Changes and Energy

The physical state of a substance (solid, liquid, gas) significantly affects its energy content. For example, converting liquid water (H2O(l)) to water vapor (H2O(g)) requires energy input, known as the enthalpy of vaporization. Therefore, if a reaction produces water in the gaseous state instead of the liquid state, the overall energy change (ΔH) will be influenced by this additional energy requirement.
Video consigliato:
Percorso guidato
01:46
Entropy in Phase Changes

Combustion Reactions

Combustion reactions involve the reaction of a substance with oxygen to produce heat and light, typically resulting in the formation of carbon dioxide and water. The products' states (gas or liquid) can affect the reaction's enthalpy change. In the case of methanol combustion, producing water vapor instead of liquid water would likely increase the energy released, as more energy is required to form gaseous products.
Video consigliato:
Percorso guidato
02:24
Combustion Apparatus
Pratica correlata
Domanda del libro di testo

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 (c) The decomposition of KClO3 proceeds spontaneously when it is heated. Do you think that the reverse reaction, the formation of KClO3 from KCl and O2, is likely to be feasible under ordinary conditions? Explain your answer.

559
views
Domanda del libro di testo

Consider the combustion of liquid methanol, CH3OH(l): CH3OH(l) + 3/2 O2(g) → CO2(g) + 2 H2O(l) ΔH = -726.5 kJ (b) Balance the forward reaction with whole-number coefficients. What is ΔH for the reaction represented by this equation?

706
views
Domanda del libro di testo

Consider the decomposition of liquid benzene, C6H6(l), to gaseous acetylene, C2H2(g): C6H6(l) → 3 C2H2(g) ΔH = +630 kJ (c) Which is more likely to be thermodynamically favored, the forward reaction or the reverse reaction?

344
views
Domanda del libro di testo

Consider the decomposition of liquid benzene, C6H6(l), to gaseous acetylene, C2H2(g): C6H6(l) → 3 C2H2(g) ΔH = +630 kJ (a) What is the enthalpy change for the reverse reaction?

803
views
Domanda del libro di testo

Consider the decomposition of liquid benzene, C6H6(l), to gaseous acetylene, C2H2(g): C6H6(l) → 3 C2H2(g) ΔH = +630 kJ (b) What is H for the formation of 1 mol of acetylene?

373
views
Domanda del libro di testo

Consider the combustion of liquid methanol, CH3OH(l): CH3OH(l) + 3/2 O2(g) → CO2(g) + 2 H2O(l) ΔH = -726.5 kJ (a) What is the enthalpy change for the reverse reaction?

744
views