The complete combustion of methane, CH 4 (g), to form H 2 O(l) and CO 2 (g) at constant pressure releases 890 kJ of heat per mole of CH 4 . (b) Draw an enthalpy diagram for the reaction.

hi everyone. This problem reads at constant pressure. The following reaction releases 1255.8 kg jewels of energy provide the correct entropy diagram for the reaction. Okay, so we want to draw a entropy dia program which is also referred to as a reaction profile. And for a reaction profile it shows the progress of a chemical reaction as a function of potential energy. All right. So, we're going to do our reaction profile here and we're going to have our reaction progress. Okay. And potential energy. All right. And our reaction progress is in time. Alright, so here we notice that our reaction is releasing energy and what that means is our change in entropy is negative. 1,255.8 kila jules. Okay, So for an exotic thermic reaction profile, the potential energy of the products is lower than the reactant. Alright, so with our reaction profile we have our reactant since and then we have our transition state and then we have our products. Okay, so we're right here reactant since and products. All right. Now this space here, this space here is our activation energy and this space here is our change and entropy and our product our initial energy Excuse me, are potential energy of the product is lower than the reactant and this gives us that negative value. Okay, and so this is going to be the correct entropy diagram for this reaction. That's it for this problem. I hope this is helpful

Ch.5 - Thermochemistry

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Brown 14th Edition

Ch.5 - Thermochemistry

Problem 39b

Chapter 5, Problem 39b

The complete combustion of methane, CH₄(g), to form H₂O(l) and CO₂(g) at constant pressure releases 890 kJ of heat per mole of CH₄. (b) Draw an enthalpy diagram for the reaction.

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Draw a horizontal line to represent the enthalpy level of the reactants, which is methane (CH_4) and oxygen (O_2).

Draw another horizontal line below the reactants' line to represent the enthalpy level of the products, which are carbon dioxide (CO_2) and water (H_2O).

Label the vertical distance between the reactants and products as the change in enthalpy (ΔH), which is -890 kJ/mol, indicating an exothermic reaction.

Add an arrow pointing downward from the reactants' line to the products' line to show the release of energy.

Label the reactants' line with 'CH_4 + 2O_2' and the products' line with 'CO_2 + 2H_2O'.

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Key Concepts

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

Enthalpy (H)

Enthalpy is a thermodynamic property that represents the total heat content of a system at constant pressure. It is defined as the sum of the internal energy and the product of pressure and volume (H = U + PV). In chemical reactions, changes in enthalpy (ΔH) indicate whether a reaction is exothermic (releases heat) or endothermic (absorbs heat), which is crucial for understanding energy changes during combustion.

Combustion Reaction

A combustion reaction is a chemical process in which a substance (typically a hydrocarbon) reacts with oxygen to produce carbon dioxide and water, releasing energy in the form of heat. In the case of methane (CH4), its complete combustion yields CO2 and H2O, and is characterized by a significant release of energy, as indicated by the 890 kJ of heat released per mole of CH4 in the question.

Enthalpy Diagram

An enthalpy diagram visually represents the changes in enthalpy during a chemical reaction. It typically shows the enthalpy of the reactants and products, along with the enthalpy change (ΔH) for the reaction. For the combustion of methane, the diagram would illustrate the higher enthalpy of the reactants compared to the lower enthalpy of the products, indicating the exothermic nature of the reaction and the energy released.

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Suppose that the gas-phase reaction 2 NO(g) + O2(g) → 2 NO2(g) were carried out in a constant-volume container at constant temperature. (a) Would the measured heat change represent _x001F_H or _x001F_E? (b) If there is a difference, which quantity is larger for this reaction? (c) Explain your answer to part (b).

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A gas is confined to a cylinder under constant atmospheric pressure, as illustrated in Figure 5.4. When 0.49 kJ of heat is added to the gas, it expands and does 214 J of work on the surroundings. What are the values of H and E for this process?

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Textbook Question

The complete combustion of methane, CH₄(g), to form H₂O(l) and CO₂(g) at constant pressure releases 890 kJ of heat per mole of CH₄. (a) Write a balanced thermochemical equation for this reaction.

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The decomposition of sodium bicarbonate (baking soda), NaHCO₃(s), into Na₂CO₃(s), H₂O(l), and CO₂(g) at constant pressure requires the addition of 85 kJ of heat per two moles of NaHCO₃. (a) Write a balanced thermochemical equation for the reaction.

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The complete combustion of methane, CH4(g), to form H2O(l) and CO2(g) at constant pressure releases 890 kJ of heat per mole of CH4. (b) Draw an enthalpy diagram for the reaction.

Verified Solution

Key Concepts

Enthalpy (H)

Combustion Reaction

Enthalpy Diagram

The complete combustion of methane, CH₄(g), to form H₂O(l) and CO₂(g) at constant pressure releases 890 kJ of heat per mole of CH₄. (b) Draw an enthalpy diagram for the reaction.