Given the following equilibrium system, what will occur if the system is subjected to an increase in temperature?
[tex]CuCl_4^{2-}(a q) green \rightleftharpoons Cu^{2+}+(a q) blue+4 Cl^{1-}(a q)+ energy[/tex]
A. Keq will decrease
B. The solution will turn more blue
C. The solution will shift right
D. Nothing will change
Answer (2)
Increasing the temperature shifts the equilibrium to the right.
The solution turns more blue as more C u 2 + is produced.
K e q increases as the concentration of products increases.
Therefore, the solution will turn more blue and shift right.
Explanation
Analyzing the Equilibrium System The given equilibrium system is:
C u C l 4 2 − ( a q ) g ree n ⇌ C u 2 + ( a q ) b l u e + 4 C l 1 − ( a q ) + energy
Applying Le Chatelier's Principle We are increasing the temperature of the system. According to Le Chatelier's principle, if we increase the temperature of a system at equilibrium, the system will shift in the direction that absorbs heat. In this case, energy is released (or appears as a product) in the forward reaction, meaning the reverse reaction absorbs energy. However, the problem states that energy is a product, which means the forward reaction is exothermic and the reverse reaction is endothermic. Therefore, increasing the temperature will favor the forward reaction (the one that produces C u 2 + and C l 1 − ).
Determining the Shift in Equilibrium Since the forward reaction is favored, the equilibrium will shift to the right. This means more C u 2 + and C l 1 − will be produced.
Analyzing the Color Change The C u 2 + ion is blue. Therefore, if the equilibrium shifts to the right, the concentration of C u 2 + will increase, and the solution will turn more blue.
Analyzing the Change in Keq The equilibrium constant, K e q , is a ratio of the concentrations of products to reactants at equilibrium. Since the forward reaction is favored, the concentration of products ( C u 2 + and C l 1 − ) will increase, and the concentration of the reactant ( C u C l 4 2 − ) will decrease. Therefore, K e q will increase.
Conclusion Based on the analysis, the correct statements are:
The solution will turn more blue.
The solution will shift right.
Examples
Le Chatelier's principle is widely used in industrial chemistry to optimize reaction conditions. For example, in the Haber-Bosch process for synthesizing ammonia ( N 2 + 3 H 2 ⇌ 2 N H 3 + h e a t ), increasing the pressure favors the forward reaction, leading to a higher yield of ammonia. Similarly, controlling the temperature is crucial, as the reaction is exothermic, and lower temperatures favor ammonia production. However, very low temperatures slow down the reaction, so a compromise temperature is used to achieve a reasonable rate and yield.
Increasing the temperature of the equilibrium system causes the reaction to shift to the right, producing more blue C u 2 + ions. This results in the solution becoming more blue and increasing the equilibrium constant. Thus, the correct answer is B. The solution will turn more blue.
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