Moderate

The following equilibrium exists in aqueous solution CH3COOH ⇌ CH3COO- H+. If dilute HCl is added without a change in temperature then

Correct answer: A. Concentration of CH3COO- will decrease

  • A. Concentration of CH3COO- will decrease
  • B. The equilibrium constant will increase
  • C. Concentration of CH3COO- will increase
  • D. The equilibrium constant will decrease

Explanation

When HCl is added, it contributes chloride ions (Cl-) to the solution. The common ion effect predicts that the presence of additional chloride ions from HCl will suppress the dissociation of CH3COO- ions. This is because the equilibrium will shift to the left to counteract the increase in the concentration of the common ion (Cl-). As a result, the concentration of CH3COO- ions will decrease.

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About Chemical Equilibrium

Reversible reactions reach dynamic equilibrium when forward and reverse rates become equal, and Le Chatelier's principle predicts the effect of changing concentration, pressure or temperature. The chapter also covers solubility product, the common ion effect, buffer action and the conditions used in Haber's process, with equilibrium shifts distinguished from changes in the equilibrium constant.

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