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Chapter 13: Problem 82

Consider the reaction $$ \mathrm{Fe}^{3+}(a q)+\mathrm{SCN}^{-}(a q) \rightleftharpoons \mathrm{FeSCN}^{2+}(a q) $$ How will the equilibrium position shift if a. water is added, doubling the volume? b. \(\mathrm{AgNO}_{3}(a q)\) is added? (AgSCN is insoluble.) c. \(\mathrm{NaOH}(a q)\) is added? \(\left[\mathrm{Fe}(\mathrm{OH})_{3}\right.\) is insoluble.] d. \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}(a q)\) is added?

Short Answer

Expert verified
a. The equilibrium position will shift to the right, favoring the formation of FeSCN²⁺, due to the decrease in concentrations caused by the addition of water. b. The equilibrium position will shift to the left, favoring the formation of Fe³⁺ and SCN⁻ ions, due to the removal of SCN⁻ ions by the formation of insoluble AgSCN. c. The equilibrium position will shift to the left, favoring the formation of Fe³⁺ and SCN⁻ ions, due to the removal of Fe³⁺ ions by the formation of insoluble Fe(OH)₃. d. The equilibrium position will shift to the right, favoring the formation of FeSCN²⁺, due to the increase in Fe³⁺ concentration caused by the addition of Fe(NO₃)₃.

Step by step solution

01

Addition of Water

When water is added, the volume of the solution is doubled. This results in the concentrations of all dissolved species being halved. According to Le Châtelier's principle, the equilibrium will shift in the direction where the concentration of the species is increased. In this case, the reaction will shift to the right (favoring the formation of FeSCN²⁺) to restore the original concentrations of the reactants and products. #b. Addition of AgNO3#
02

Addition of AgNO3

When AgNO3(aq) is added to the solution, Ag⁺(aq) ions in AgNO3 will react with SCN⁻(aq) ions to form insoluble AgSCN(s). This effectively removes SCN⁻ from the solution, causing a decrease in its concentration. According to Le Châtelier's principle, the reaction will shift to the left (favoring the formation of Fe³⁺ and SCN⁻ ions) to counteract the decrease in SCN⁻ concentration. #c. Addition of NaOH#
03

Addition of NaOH

When NaOH(aq) is added to the solution, OH⁻(aq) ions in NaOH will react with Fe³⁺(aq) ions to form insoluble Fe(OH)₃(s). This effectively removes Fe³⁺ from the solution, causing a decrease in its concentration. According to Le Châtelier's principle, the reaction will shift to the left (favoring the formation of Fe³⁺ and SCN⁻ ions) to counteract the decrease in Fe³⁺ concentration. #d. Addition of Fe(NO3)3#
04

Addition of Fe(NO3)3

When Fe(NO3)3(aq) is added to the solution, it will increase the concentration of Fe³⁺ ions. According to Le Châtelier's principle, the reaction will shift to the right (favoring the formation of FeSCN²⁺) to counteract the increase in Fe³⁺ concentration.

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Most popular questions from this chapter

At \(25^{\circ} \mathrm{C}\), gaseous \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) decomposes to \(\mathrm{SO}_{2}\left(\mathrm{~g}\right.\) ) and \(\mathrm{Cl}_{2}(\mathrm{~g})\) to the extent that \(12.5 \%\) of the original \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) (by moles) has decomposed to reach equilibrium. The total pressure (at equilibrium) is \(0.900\) atm. Calculate the value of \(K_{\mathrm{p}}\) for this system.

The gas arsine, \(\mathrm{AsH}_{3}\), decomposes as follows: $$ 2 \mathrm{AsH}_{3}(g) \rightleftharpoons 2 \mathrm{As}(s)+3 \mathrm{H}_{2}(g) $$ In an experiment at a certain temperature, pure \(\operatorname{AsH}_{3}(g)\) was placed in an empty, rigid, sealed flask at a pressure of \(392.0\) torr. After 48 hours the pressure in the flask was observed to be constant at \(488.0\) torr. a. Calculate the equilibrium pressure of \(\mathrm{H}_{2}(\mathrm{~g})\). b. Calculate \(K_{\mathrm{p}}\) for this reaction.

Consider the following reactions: \(\mathrm{H}_{2}(g)+\mathrm{I}_{2}(g) \longrightarrow 2 \mathrm{HI}(g)\) and \(\mathrm{H}_{2}(g)+\mathrm{I}_{2}(s) \longrightarrow 2 \mathrm{HI}(g)\) List two property differences between these two reactions that relate to equilibrium.

Le Châtelier's principle is stated (Section \(13.7)\) 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.

A \(1.604-g\) sample of methane \(\left(\mathrm{CH}_{4}\right)\) gas and \(6.400 \mathrm{~g}\) oxygen gas are sealed into a 2.50-L vessel at \(411^{\circ} \mathrm{C}\) and are allowed to reach equilibrium. Methane can react with oxygen to form gaseous carbon dioxide and water vapor, or methane can react with oxygen to form gaseous carbon monoxide and water vapor. At equilibrium, the pressure of oxygen is \(0.326 \mathrm{~atm}\), and the pressure of water vapor is \(4.45\) atm. Calculate the pressures of carbon monoxide and carbon dioxide present at equilibrium.
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