For each generic reaction, determine the value of ΔH 2 in terms of ΔH 1 . a. A + B → 2 C ΔH 1 2 C→ A + B ΔH 2 = ?

welcome back everyone in this example we need to use his law to draw a diagram or an entropy diagram specifically for these substances present in the below reactions. So for our first given reaction we have why acting as a re agent. And this produces Z as a product. Were given a entropy value which corresponds to negative 120 kg joules. And then in our second reaction given from the prompt we have Z. Which now is being consumed as a reactant to form X. As a product corresponding to an entropy value of negative 70 kg joules. So we should recall first that delta H, which is our value for N. Therapy corresponds to the heat energy that is absorbed or evolved in a reaction. Now for us to tell whether the heat energy here is absorbed or evolved. We want to recognize that our entropy is negative for both reactions. And because entropy is negative, we can say that therefore, we can say that energy or he is released, meaning that we have an exhaust thermic reaction here. So we have two eggs. A thermic reactions now are prompt states that we should use Hess's law when drawing our diagram for our final answer. And we should recall that according to his law. If a reaction can take place By more than one route and initial and final conditions remain the same, then our total entropy change will remain the same. So we need to use a diagram to depict what is going on according to Hess's law with our given reaction. And as we can see here we have Z being produced as a product in the first given reaction where it's done being consumed as a reactant in the second reaction. And ultimately this means that because Z is both produced as a product in the first given reaction and then consumed as a reactant In the second given reaction, we can say that therefore Z is an intermediate. And so according to our second reaction, X is our final product. So in our diagram before we can actually draw the diagram, we want to write out a third reaction for the formation of why as a reactant to form X as the final product. And we should recall that using his law, this would be another route of getting to this product. And this means that our total change in entropy should remain the same. So we would say that our change in entropy is going to equal the sum from our first entropy of our reaction being negative 120 kg joules added to the sum of the entropy from the second given reaction in the prompt being negative kg joules. And so taking the sum here we get a change in entropy equal to a value of negative 190 kg joules. And so as we've outlined according to Hess's law above the total change in entropy going from reactant Y. Two product X is equal to a value of negative 190 kg joules. And this total change in entropy remains the same. Whether we go from reactant Y to form our intermediate Z. Corresponding to the change in entropy given in the prompt as negative 120 kg joules. Which is then added to the change in entropy going from Z as a reactant to our final product X. Which corresponded to the change in entropy equal to negative 70 kg joules. As given in the prompt. And so this diagram here would be our final answer Hess's law according to the given substances in our reactions. And so this would correspond to choice D in our multiple choice as our final answer. So I hope that everything that I reviewed was clear. But if you have any questions just lead them down below and I will see everyone in the next practice video.

Ch.7 - Thermochemistry

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Tro 5th Edition

Ch.7 - Thermochemistry

Problem 77a

Chapter 7, Problem 77a

For each generic reaction, determine the value of ΔH₂ in terms of ΔH₁.
a. A + B → 2 C ΔH₁
2 C→ A + B ΔH₂ = ?

Verified step by step guidance

insert step 1> Identify the type of reaction given in the problem. The first reaction is A + B \rightarrow 2C with an enthalpy change of \Delta H_1.

insert step 2> Recognize that the second reaction is the reverse of the first reaction: 2C \rightarrow A + B.

insert step 3> Understand that reversing a chemical reaction changes the sign of the enthalpy change. Therefore, \Delta H_2 will be the negative of \Delta H_1.

insert step 4> Express \Delta H_2 in terms of \Delta H_1: \Delta H_2 = -\Delta H_1.

insert step 5> Conclude that the enthalpy change for the reverse reaction is the negative of the enthalpy change for the forward reaction.

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Key Concepts

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

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). Understanding ΔH is crucial for predicting the energy changes associated with chemical reactions.

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is the same, regardless of the number of steps taken to achieve the reaction. This principle allows us to calculate the enthalpy change of a reaction by using the enthalpy changes of related reactions, making it essential for determining ΔH2 in terms of ΔH1.

Reversible Reactions

Reversible reactions can proceed in both forward and reverse directions, allowing for the establishment of equilibrium. The relationship between the forward and reverse reactions is critical in determining the enthalpy changes, as the enthalpy change for the reverse reaction is equal in magnitude but opposite in sign to that of the forward reaction.

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Reversible Changes in Matter

Related Practice

Textbook Question

Zinc metal reacts with hydrochloric acid according to the balanced equation: Zn(s) + 2 HCl(aq) → ZnCl₂(aq) + H₂(g) When 0.103 g of Zn(s) is combined with enough HCl to make 50.0 mL of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 22.5 °C to 23.7 °C. Find ΔH_rxn for this reaction as written. (Use 1.0 g/mL for the density of the solution and 4.18 J/g•°C as the specific heat capacity.)

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Textbook Question

Determine whether each process is exothermic or endothermic and indicate the sign of ΔH. a. natural gas burning on a stove b. isopropyl alcohol evaporating from skin c. water condensing from steam Indicate the sign of ΔH for the following processes.

Textbook Question

Instant cold packs used to ice athletic injuries on the field contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves according to the endothermic reaction: NH₄NO₃(s) → NH₄⁺(aq) + NO₃^– (aq) In order to measure the enthalpy change for this reaction, 1.25 g of NH₄NO₃ is dissolved in enough water to make 25.0 mL of solution. The initial temperature is 25.8 °C and the final temperature (after the solid dissolves) is 21.9 °C. Calculate the change in enthalpy for the reaction in kJ. (Use 1.0 g/mL as the density of the solution and 4.18 J/g•°C as the specific heat capacity.)

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Textbook Question

For each generic reaction, determine the value of ΔH₂ in terms of ΔH₁.

b. A + 1/2 B → C ΔH₁

2 A + B → 2 C ΔH₂ = ?

Textbook Question

For each generic reaction, determine the value of ΔH₂ in terms of ΔH₁.

c. A → B + 2 C ΔH₁

1/2 B + C → 1/2 A ΔH₂ = ?

Textbook Question

Consider the generic reaction:

A + 2 B → C + 3 D ΔH = 155 kJ