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 (a) What is the enthalpy change for the reverse reaction?

Hey everyone. So here it says, considered the dissolution of calcium chloride determine the entropy that change in entropy for the reverse reaction. Alright, so here we have calcium chloride solid breaking down to give us calcium ion plus two chloride ions. Here, the entropy of reaction for this is negative 81.5 kg per mole. Here we have to do the reverse of it. So now our products will become our reactant. So calcium ion plus two chloride ions well combined together to give me my one mole of calcium chloride solid. Now remember that when you reverse the reaction, you also are going to have to reverse the sign of Delta H. Here it started off as negative 81.5 Na becomes positive 81.5 and it'll still be killer joules per mole. So this would be my final answer for the reverse reaction for the dissolution of calcium chloride.

Ch.5 - Thermochemistry

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Brown 14th Edition

Ch.5 - Thermochemistry

Problem 48a

Chapter 5, Problem 48a

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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Identify the forward reaction and its enthalpy change: The decomposition of liquid benzene (C₆H₆(l)) into gaseous acetylene (C₂H₂(g)) has an enthalpy change (ΔH) of +630 kJ.

Understand the concept of enthalpy change for reverse reactions: The enthalpy change for the reverse reaction is equal in magnitude but opposite in sign to the enthalpy change of the forward reaction.

Write the equation for the reverse reaction: 3 C₂H₂(g) → C₆H₆(l).

Determine the sign of ΔH for the reverse reaction: Since the forward reaction is endothermic (+630 kJ), the reverse reaction will be exothermic, which means ΔH will be negative.

Calculate the magnitude of ΔH for the reverse reaction: It will be -630 kJ, indicating that energy is released when acetylene converts back to benzene.

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Key Concepts

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

Enthalpy Change

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). In the given reaction, the positive ΔH value of +630 kJ signifies that the decomposition of benzene into acetylene requires energy input.

Reverse Reaction

The reverse reaction is simply the process of converting products back into reactants. According to the principle of conservation of energy, the enthalpy change for the reverse reaction is equal in magnitude but opposite in sign to that of the forward reaction. Therefore, if the forward reaction has a ΔH of +630 kJ, the reverse reaction will have a ΔH of -630 kJ.

Thermodynamic Principles

Thermodynamic principles govern the relationships between heat, work, and energy in chemical reactions. These principles help predict how energy is transferred during reactions. Understanding these principles is crucial for calculating enthalpy changes and determining the feasibility of reactions under different conditions.

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Related Practice

Textbook Question

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?

Textbook Question

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?

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Textbook Question

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.

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?

Textbook Question

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?

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.

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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Key Concepts

Enthalpy Change

Reverse Reaction

Thermodynamic Principles

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?