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Ch.16 - Acid-Base Equilibria
Chapter 16, Problem 50

Write the chemical equation and the Ka expression for the acid dissociation of each of the following acids in aqueous solution. First show the reaction with H+(a)q as a product and then with the hydronium ion: (a) C6H5COOH (b) HCO3-

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Identify the acid and its dissociation in water: Benzoic acid (C6H5COOH) dissociates in water to produce hydrogen ions (H^+) and benzoate ions (C6H5COO^-).
Write the chemical equation for the dissociation of benzoic acid with H^+ as a product: C6H5COOH (aq) \rightleftharpoons H^+ (aq) + C6H5COO^- (aq).
Write the Ka expression for the dissociation with H^+ as a product: K_a = \frac{[H^+][C6H5COO^-]}{[C6H5COOH]}.
Write the chemical equation for the dissociation of benzoic acid with the hydronium ion (H3O^+) as a product: C6H5COOH (aq) + H2O (l) \rightleftharpoons H3O^+ (aq) + C6H5COO^- (aq).
Write the Ka expression for the dissociation with H3O^+ as a product: K_a = \frac{[H3O^+][C6H5COO^-]}{[C6H5COOH]}.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acid Dissociation

Acid dissociation refers to the process by which an acid donates a proton (H+) to a water molecule, resulting in the formation of a hydronium ion (H3O+). This process is fundamental in understanding the behavior of acids in aqueous solutions, as it determines the strength of the acid and its ability to increase the concentration of H3O+ in the solution.
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Ka Expression

The acid dissociation constant (Ka) is a quantitative measure of the strength of an acid in solution. It is defined as the ratio of the concentration of the products (hydronium ion and the conjugate base) to the concentration of the undissociated acid at equilibrium. The Ka expression provides insight into how readily an acid donates protons, with larger values indicating stronger acids.
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Chemical Equations

A chemical equation represents the reactants and products of a chemical reaction using their chemical formulas. In the context of acid dissociation, the equation illustrates how an acid, such as benzoic acid (C6H5COOH), dissociates in water to form hydronium ions and its conjugate base. Writing these equations correctly is essential for understanding the reaction dynamics and calculating related properties like pH.
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