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Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium
Chapter 18, Problem 27a

Ideal gases A (red spheres) and B (blue spheres) occupy two separate bulbs. The contents of both bulbs constitute the initial state of an isolated system. Consider the process that occurs when the stopcock is opened.
Two bulbs with yellow spheres (gas A) and green spheres (gas B) separated by a stopcock.
(a) Sketch the final (equilibrium) state of the system.

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Key Concepts

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

Ideal Gas Law

The Ideal Gas Law describes the relationship between pressure, volume, temperature, and the number of moles of an ideal gas. It is expressed as PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature. This law helps predict how gases will behave under various conditions, particularly when they are allowed to mix or expand.
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Equilibrium State

An equilibrium state in a system occurs when the concentrations of the gases become uniform throughout the available volume after the stopcock is opened. At this point, the rates of the forward and reverse processes (e.g., diffusion of gas A and gas B) are equal, resulting in no net change in the concentrations of the gases. Understanding this concept is crucial for predicting the final distribution of gases in the system.
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Diffusion

Diffusion is the process by which gas molecules spread from areas of higher concentration to areas of lower concentration. In the context of the question, when the stopcock is opened, gas A (yellow spheres) and gas B (green spheres) will diffuse into each other's space until they are evenly distributed. This process is driven by the random motion of gas particles and is essential for understanding how gases mix in an isolated system.
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Related Practice
Textbook Question

Spinach contains a lot of iron but is not a good source of dietary iron because nearly all the iron is tied up in the oxalate complex [Fe(C2O4)3]3-.

(b) Under the acidic conditions in the stomach, the Fe3+ concentration should be greater because of the reaction

[Fe(C2O4)3]3-(aq) + 6 H3O+(aq) ⇌ Fe3+(aq) + 3 H2C2O4(aq) + 6 H2O(l)

Show, however, that this reaction is nonspontaneous under standard-state conditions. (For H2C2O4, Ka1 = 5.9 × 10-2 and Ka2 = 6.4 × 10-5.)

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Textbook Question

Formation constants for the ammonia and ethylenediamine complexes of nickel(II) indicate that Ni(en)32+ is much more

stable than Ni(NH3)62+:

(1) <REACTION>

(2) <REACTION>

The enthalpy changes for the two reactions, ΔH°1 and ΔH°2, should be about the same because both complexes have six Ni﹣N bonds. 

(c) Assuming that ΔH°2 - ΔH°1 is zero, calculate the value of ΔS°2 - ΔS°1.

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Textbook Question
Consider the gas-phase reaction of AB3 and A2 molecules:

(a) Write a balanced equation for the reaction. (b) What is the sign of the entropy change for the reaction?
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Textbook Question

Ideal gases A (red spheres) and B (blue spheres) occupy two separate bulbs. The contents of both bulbs constitute the initial state of an isolated system. Consider the process that occurs when the stopcock is opened.

(b) What are the signs ( + , - , or 0) of ∆H, ∆S, and ∆G for this process? Explain.

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Textbook Question

Ideal gases A (red spheres) and B (blue spheres) occupy two separate bulbs. The contents of both bulbs constitute the initial state of an isolated system. Consider the process that occurs when the stopcock is opened.

(c) How dpes this process illustrate the second law of thermodynamics?

326
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Textbook Question

Ideal gases A (red spheres) and B (blue spheres) occupy two separate bulbs. The contents of both bulbs constitute the initial state of an isolated system. Consider the process that occurs when the stopcock is opened.

(d) Relate each of the pictures to the graph in Figure 18.11.

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