Consider the equilibrium B₁(aq)₂ + H₂O(l)₂ ⇌ HB⁺₁(aq)₂ + OH⁻₁(aq)₂. Suppose that a salt of HB⁺₁(aq)₂ is added to a solution of B₁(aq)₂ at equilibrium. (a) Will the equilibrium constant for the reaction increase, decrease, or stay the same? (b) Will the concentration of B(aq) increase, decrease, or stay the same?

Verified step by step guidance

1. Identify the type of equilibrium reaction: The given reaction is a base dissociation reaction where B(aq) acts as a base, accepting a proton from water to form HB⁺(aq) and OH⁻(aq).
2. Understand the effect of adding a salt: Adding a salt of HB⁺(aq) introduces more HB⁺ ions into the solution. This is an example of Le Chatelier's Principle, where the system will adjust to counteract the change.
3. Analyze the effect on equilibrium constant: The equilibrium constant (K) is only affected by changes in temperature. Since adding a salt does not change the temperature, the equilibrium constant will stay the same.
4. Predict the shift in equilibrium: According to Le Chatelier's Principle, adding more HB⁺(aq) will shift the equilibrium to the left to reduce the concentration of HB⁺(aq), thus increasing the concentration of B(aq).
5. Conclude the effect on B(aq) concentration: As the equilibrium shifts to the left, the concentration of B(aq) will increase as the system tries to re-establish equilibrium.

Key Concepts

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the system will respond to counteract the change and restore a new equilibrium. In this case, adding a salt of HB⁺ will increase the concentration of HB⁺ in the solution, prompting the equilibrium to shift to the left to reduce this change.

Equilibrium Constant (K)

The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. It remains constant unless the temperature changes. Adding HB⁺ does not change the temperature, so the value of K will stay the same, even though the concentrations of the species may shift.

Concentration Changes in Equilibrium

In a chemical equilibrium, the concentrations of reactants and products remain constant over time. However, when a substance is added to the system, such as HB⁺, it can affect the concentrations of other species. In this scenario, the addition of HB⁺ will shift the equilibrium to the left, leading to a decrease in the concentration of B₁ as it reacts to form more reactants.