Consider the decomposition of liquid benzene, C 6 H 6 (l), to gaseous acetylene, C 2 H 2 (g): C 6 H 6 (l) → 3 C2H 2 (g) ΔH = +630 kJ (c) Which is more likely to be thermodynamically favored, the forward reaction or the reverse reaction?

Hey there, welcome back. So here we're being asked is the forward or reverse reaction of this reaction. Right here. More thermo dynamically favored. Okay, so notice that here we have a negative delta H. Which means we are releasing energy. Right? So this reaction is releasing energy. And what does thermo dynamically favored mean? It means that the less energy you have, the more stable you are so less energy more stable. So you're more thermo dynamically favored. Um If you release energy and basically go from a high energy state to a low energy state, right? It's always more favorable that way thermo dynamically. So here that's exactly what's happening. So in this delta age reaction that's negative obviously is for the forward as as written, right? For the forward reaction, it is favored because it is negative. Now what happens to delta H when we reverse the reaction? Well, it's gonna the value is gonna stay exactly the same. It's just gonna be positive. 283 kg jewels, right? Per mole? Which means what? Which means that this reaction is actually going to be gaining energy and becoming less stable. Right? So it's going to be gaining energy which means less stable. And that is not thermo dynamically favored. Okay, so which one is more thermodynamic thermodynamic lee favored is going to be the reverse one. Right? The reverse because the delta H. Is negative. If it was positive then the opposite would be true then the reverse one would be more favorable. But here the way that is threatened for this specific reaction with a negative delta H. A reaction forward direction is more favored. Alright, folks, thank you so much for watching.

Ch.5 - Thermochemistry

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Brown 15th Edition

Ch.5 - Thermochemistry

Problem 48c

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Chapter 5, Problem 48c

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?

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Identify the sign of the enthalpy change (ΔH) for the reaction. A positive ΔH indicates that the reaction is endothermic, meaning it absorbs heat from the surroundings.

Understand that thermodynamically favored reactions are generally those that release energy (exothermic reactions), where ΔH is negative, as they lead to a decrease in the system's enthalpy, making the products more stable than the reactants.

Compare the enthalpy change of the forward reaction, which is +630 kJ, indicating that it is endothermic and requires energy input to proceed.

Consider the reverse reaction, where the sign of ΔH would be negative (-630 kJ), suggesting that it is exothermic. This reaction would release energy, making it more likely to occur spontaneously under standard conditions.

Conclude that the reverse reaction, forming liquid benzene from gaseous acetylene, is more likely to be thermodynamically favored due to its exothermic nature.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Thermodynamics and Reaction Favorability

Thermodynamics is the study of energy transformations, particularly how energy changes influence the direction of chemical reactions. A reaction is thermodynamically favored if it leads to a decrease in free energy, typically indicated by a negative change in Gibbs free energy (ΔG). In this context, the forward reaction's positive enthalpy change (ΔH = +630 kJ) suggests it absorbs heat, which may affect its favorability.

Enthalpy and Reaction Energy

Enthalpy (H) is a measure of the total energy of a thermodynamic system, including internal energy and the energy required to make room for it by displacing its environment. A positive ΔH indicates that the reaction is endothermic, meaning it requires energy input. Understanding the enthalpy change helps predict whether a reaction will proceed spontaneously under given conditions.

Entropy and Disorder

Entropy (S) is a measure of the disorder or randomness in a system. In chemical reactions, an increase in the number of gas molecules typically leads to an increase in entropy, which can favor the reaction despite a positive enthalpy change. In this case, the decomposition of liquid benzene into gaseous acetylene increases the number of gas molecules, potentially making the forward reaction more favorable from an entropy perspective.

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Textbook Question

Consider the combustion of isopropanol, C₃H₇OH(l), which is the primary component of rubbing alcohol: C₃H₇OH(l) + 9/2 O₂(g) → 3 CO₂(g) + 4 H₂O(l) ΔH = -2248 kJ (b) Balance the forward reaction with whole-number coefficients. What is ΔH for the reaction represented by this equation?

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Textbook Question

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?

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Textbook Question

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?

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Textbook Question

Consider the decomposition of liquid benzene, C₆H₆(l), to gaseous acetylene, C₂H₂(g): C₆H₆(l) → 3 C2H₂(g) ΔH = +630 kJ (d) If C₆H₆(g) were consumed instead of C₆H₆(l), would you expect the magnitude of ΔH to increase, decrease, or stay the same? Explain.

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Textbook Question

b. What are the units of specific heat?

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Textbook Question

Two solid objects, A and B, are placed in boiling water and allowed to come to the temperature of the water. Each is then lifted out and placed in separate beakers containing 1000 g of water at 10.0 °C. Object A increases the water temperature by 3.50 °C; B increases the water temperature by 2.60 °C. (a) Which object has the larger heat capacity?

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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?

Verified Solution

Key Concepts

Thermodynamics and Reaction Favorability

Enthalpy and Reaction Energy

Entropy and Disorder

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?