Consider the following chemical reaction in equilibrium:
[tex]$CH_3 COOH \Leftrightarrow CH_3 COO^{-}(a q)+H^{+}(a q)$[/tex]
What will happen to the chemical equilibrium if [tex]$MgCl _2$[/tex] is added?
A. The chemical equilibrium of the system will be unaffected.
B. The chemical equilibrium of the system will shift to the right to favor the forward reaction.
C. The chemical equilibrium of the system will be damaged irreversibly.
Answer (2)
M g C l 2 dissociates into M g 2 + and C l − ions in water.
M g 2 + ions interact with C H 3 CO O − ions, reducing their concentration.
According to Le Chatelier's principle, the equilibrium shifts to counteract the decrease in C H 3 CO O − concentration.
The chemical equilibrium shifts to the right, favoring the forward reaction. The answer is: The chemical equilibrium of the system will shift to the right to favor the forward reaction.
Explanation
Problem Analysis The chemical reaction in equilibrium is: C H 3 COO H ⇔ C H 3 CO O − ( a q ) + H + ( a q ) We need to determine what happens to the equilibrium when M g C l 2 is added.
Dissociation of M g C l 2 and Interaction with Acetate M g C l 2 is an ionic compound that dissociates in water into magnesium ions ( M g 2 + ) and chloride ions ( 2 C l − ): M g C l 2 ( s ) → M g 2 + ( a q ) + 2 C l − ( a q ) The magnesium ions ( M g 2 + ) will interact with the acetate ions ( C H 3 CO O − ) in the solution. Magnesium acetate ( M g ( C H 3 COO ) 2 ) is a soluble salt, but the interaction between M g 2 + and C H 3 CO O − will still reduce the concentration of free C H 3 CO O − ions in the solution.
Applying Le Chatelier's Principle According to Le Chatelier's principle, if a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress. In this case, the stress is the decrease in the concentration of C H 3 CO O − ions due to the addition of M g C l 2 . To counteract this decrease, the equilibrium will shift to the right, favoring the forward reaction to produce more C H 3 CO O − and H + .
Conclusion Therefore, the chemical equilibrium will shift to the right to favor the forward reaction.
Examples
Consider a scenario where you're brewing beer. The equilibrium of various chemical reactions determines the final taste and alcohol content. Adding M g C l 2 can be seen as similar to adding an ingredient that affects the concentration of certain ions, thus shifting the equilibrium and altering the beer's characteristics. Understanding Le Chatelier's principle helps brewers predict and control these shifts to achieve the desired outcome. This principle is also crucial in various industrial processes, such as optimizing the yield of chemical reactions or controlling the purity of products.
The addition of magnesium chloride (MgCl₂) decreases the concentration of acetate ions (CH₃COO⁻) by forming magnesium acetate. According to Le Chatelier's principle, this decrease causes the equilibrium to shift to the right to favor the forward reaction. Thus, the correct answer is option B, indicating that the chemical equilibrium will shift to the right.
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