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Chapter 12: Problem 8

Le Châtelier's principle is stated (Section \(12-7\) ) as follows: "If a change is imposed on a system at equilibrium, the position of the equilibrium will shift in a direction that tends to reduce that change." The system \(\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \rightleftharpoons 2 \mathrm{NH}_{3}(g)\) is used as an example in which the addition of nitrogen gas at equilibrium results in a decrease in \(\mathrm{H}_{2}\) concentration and an increase in \(\mathrm{NH}_{3}\) concentration. In the experiment the volume is assumed to be constant. On the other hand, if \(\mathrm{N}_{2}\) is added to the reaction system in a container with a piston so that the pressure can be held constant, the amount of \(\mathrm{NH}_{3}\) actually could decrease, and the concentration of \(\mathrm{H}_{2}\) would increase as equilibrium is reestablished. Explain how this can happen. Also, if you consider this same system at equilibrium, the addition of an inert gas, holding the pressure constant, does affect the equilibrium position. Explain why the addition of an inert gas to this system in a rigid container does not affect the equilibrium position.

Short Answer

Expert verified
When nitrogen gas (N2) is added to the system at constant volume, the equilibrium shifts to the right, causing a decrease in H2 concentration and an increase in NH3 concentration. However, when pressure is held constant and N2 is added, the equilibrium shifts to the left, resulting in a decrease in NH3 and an increase in H2 concentration. Adding an inert gas at constant pressure does not change the equilibrium position because it does not directly affect the concentrations of the reactants or products. However, when an inert gas is added at constant volume, the pressure increases, but since the inert gas does not participate in the reaction, the equilibrium position and concentrations remain unchanged.

Step by step solution

01

Understanding Le Châtelier's Principle

Le Châtelier's principle states that if a change is imposed on a system at equilibrium, the position of the equilibrium will shift in a direction that tends to reduce that change. It means if we change pressure, concentration, or temperature, the system will react accordingly to reestablish the equilibrium.
02

Effect of adding nitrogen gas when volume is constant

According to the exercise, when nitrogen (N2) is added to the system with constant volume, there is a decrease in H2 concentration and an increase in NH3 concentration. This happens because the system is trying to decrease the concentration of N2 by shifting the equilibrium position to the right. In the right, N2 and H2 react to produce NH3, which causes the decrease in H2 concentration and an increase in NH3 concentration.
03

Effect of adding nitrogen gas when pressure is constant

When pressure is held constant and N2 is added, in order to maintain the constant pressure, the volume of the system will increase. As a result, an increase in volume will cause a shift in the equilibrium position that favors the side with a larger number of moles of gas particles. In this case, the left side has 4 moles of gas (1 mole of N2 and 3 moles of H2) and the right side has 2 moles of NH3. Therefore, the equilibrium position shifts towards the left (from products to reactants), reducing the amount of NH3 and increasing the H2 concentration.
04

Effect of adding an inert gas with constant pressure

When an inert gas is added to the system and pressure is held constant, the volume of the container will increase to keep the pressure constant. Adding an inert gas does not directly change the equilibrium position because it does not react with any of the components in the chemical reaction. Since the volume has increased, the gas concentrations decrease proportionally, but the equilibrium constant remains unchanged. Therefore, the equilibrium position does not change in this case.
05

Effect of adding an inert gas with constant volume

When an inert gas is added to the system and the volume is constant, the pressure in the container will increase. However, since the inert gas does not participate in the reaction, it does not change the partial pressures of the reactants or products. Therefore, the equilibrium position and the concentrations of the reactants and products remain unchanged.

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Most popular questions from this chapter

Given \(K=3.50\) at \(45^{\circ} \mathrm{C}\) for the reaction $$\mathrm{A}(g)+\mathrm{B}(g) \rightleftharpoons \mathrm{C}(g)$$ and \(K=7.10\) at \(45^{\circ} \mathrm{C}\) for the reaction $$2 \mathrm{A}(g)+\mathrm{D}(g) \rightleftharpoons \mathrm{C}(g)$$what is the value of \(K\) at the same temperature for the reaction $$ \mathrm{C}(g)+\mathrm{D}(g) \rightleftharpoons 2 \mathrm{B}(g)$$.What is the value of \(K_{\mathrm{p}}\) at \(45^{\circ} \mathrm{C}\) for the reaction? Starting with 1.50 atm partial pressures of both \(\mathrm{C}\) and \(\mathrm{D},\) what is the mole fraction of B once equilibrium is reached?

Lexan is a plastic used to make compact discs, eyeglass lenses, and bulletproof glass. One of the compounds used to make Lexan is phosgene \(\left(\mathrm{COCl}_{2}\right),\) an extremely poisonous gas. Phosgene decomposes by the reaction,$$\operatorname{COCl}_{2}(g) \rightleftharpoons \mathrm{CO}(g)+\mathrm{Cl}_{2}(g)$$,for which \(K_{\mathrm{p}}=6.8 \times 10^{-9}\) at \(100^{\circ} \mathrm{C}\). If pure phosgene at an initial pressure of 1.0 atm decomposes, calculate the equilibrium pressures of all species.

For the reaction $$\mathrm{NH}_{3}(g)+\mathrm{H}_{2} \mathrm{S}(g) \rightleftharpoons \mathrm{NH}_{4} \mathrm{HS}(s)$$,\(K=400 .\) at \(35.0^{\circ} \mathrm{C} .\) If 2.00 moles each of \(\mathrm{NH}_{3}, \mathrm{H}_{2} \mathrm{S},\) and NH,HS are placed in a 5.00 -L vessel, what mass of \(\mathrm{NH}_{4} \mathrm{HS}\) will be present at equilibrium? What is the pressure of \(\mathrm{H}_{2} \mathrm{S}\) at equilibrium?

At \(2200^{\circ} \mathrm{C}, K_{\mathrm{p}}=0.050\) for the reaction $$\mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{NO}(g)$$.What is the partial pressure of NO in equilibrium with \(\mathrm{N}_{2}\) and \(\mathrm{O}_{2}\) that were placed in a flask at initial pressures of 0.80 and 0.20 atm, respectively?

Which of the following statements is(are) true? Correct the false statement(s). a. When a reactant is added to a system at equilibrium at a given temperature, the reaction will shift right to reestablish equilibrium. b. When a product is added to a system at equilibrium at a given temperature, the value of \(K\) for the reaction will increase when equilibrium is reestablished. c. When temperature is increased for a reaction at equilibrium, the value of \(K\) for the reaction will increase. d. When the volume of a reaction container is increased for a system at equilibrium at a given temperature, the reaction will shift left to reestablish equilibrium. e. Addition of a catalyst (a substance that increases the speed of the reaction) has no effect on the equilibrium position.
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