- The dissociation of \(NH_4Cl\) increases the concentration of \(NH_4^+\) ions in the equilibrium system.
- According to Le Chatelier's Principle, increasing the concentration of a product prompts the system to shift towards the reactants to counteract the change.
- The shift reduces the added product, causing the equilibrium to move to the left.
- Therefore, the equilibrium shifts to the left, which is option (b).
- Final Answer: \(\boxed{b}\)
Explanation
- Reaction Analysis and Ion Addition
The chemical equilibrium is represented by the equation:
\[NH_4OH(aq) \rightleftharpoons NH_4^+(aq) + OH^-(aq)\]
Ammonium chloride, \(NH_4Cl\), is a strong electrolyte that dissociates completely in aqueous solution as follows:
\[NH_4Cl(aq) \rightarrow NH_4^+(aq) + Cl^-(aq)\]
By adding \(NH_4Cl\) to the reaction, we increase the concentration of ammonium ions, \(NH_4^+\), which are a product of the dissociation of \(NH_4OH\).
- Applying Le Chatelier's Principle
Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the system will adjust to counteract the change and re-establish a new equilibrium. Specifically, if the concentration of one of the products in a reaction at equilibrium is increased, the system will shift its position to favor the reactants, thereby consuming some of the added product to reach a new equilibrium state.
- Determining the Equilibrium Shift
In this system, increasing the concentration of \(NH_4^+\) ions (a product) causes the reaction to move in the direction that reduces the amount of \(NH_4^+\). This direction is towards the reactant, \(NH_4OH\). Consequently, the chemical equilibrium shifts to the left, favoring the formation of \(NH_4OH\). Therefore, the correct conclusion is that the chemical equilibrium will shift to the left. This corresponds to option (b).
Examples
In laboratory settings, scientists often use the common ion effect to control chemical reactions. For instance, if you need to reduce the hydroxide concentration of a weak base solution like ammonium hydroxide without changing the total volume of the solution, adding a salt that provides one of the conjugate ions, such as ammonium chloride, is a standard technique. This process, governed by Le Chatelier's Principle, is essential in fields like analytical chemistry and water treatment, where specific ion concentrations must be precisely managed to ensure desired reactions occur or to precipitate specific compounds out of a mixture.