Calculate the concentrations of all species present and the pH in 0.10 M solutions of the following substances. See Appendix C for values of equilibrium constants. (b) Sodium acetate, Na1CH3CO22

검증된 단계별 안내

Identify the species present in the solution: Sodium acetate (NaCH3COO) dissociates in water to form Na^+ and CH3COO^- ions.

Recognize that CH3COO^- is the conjugate base of acetic acid (CH3COOH) and can undergo hydrolysis in water to form CH3COOH and OH^-.

Write the hydrolysis equilibrium expression for CH3COO^-: CH3COO^- + H2O \(\rightleftharpoons\) CH3COOH + OH^-.

Use the equilibrium constant for the hydrolysis reaction, which is related to the K_a of acetic acid: K_b = \(\frac{K_w}{K_a}\), where K_w is the ion-product constant of water.

Set up an ICE (Initial, Change, Equilibrium) table to determine the concentrations of CH3COOH, OH^-, and CH3COO^- at equilibrium, and use the K_b expression to solve for the concentration of OH^- to find the pH.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Acid-Base Equilibria

Acid-base equilibria involve the transfer of protons (H+) between species in solution. In the case of sodium acetate, it acts as a weak base in water, where it can hydrolyze to produce acetate ions (CH3COO-) and hydroxide ions (OH-). Understanding the equilibrium between these species is crucial for calculating pH and concentrations.

Hydrolysis of Acetate Ion

The acetate ion (CH3COO-) can undergo hydrolysis in water, reacting with water to form acetic acid (CH3COOH) and hydroxide ions (OH-). This reaction is essential for determining the pH of the solution, as it establishes the equilibrium that dictates the concentration of hydroxide ions, which in turn affects the pH.

Equilibrium Constants

Equilibrium constants (K) quantify the ratio of concentrations of products to reactants at equilibrium for a given reaction. For the hydrolysis of acetate, the equilibrium constant (K_b) can be used to calculate the concentrations of all species in solution. This is vital for determining the pH, as it allows for the calculation of the extent of the hydrolysis reaction.