Write the chemical equation and the Kb expression for the reaction of each of the following bases with water: (a) dimethylamine, (CH3)2NH (b) carbonate ion, CO3^2- (c) formate ion, CHO2^-

Name: Chemistry: The Central Science
Author: Brown
ISBN: 9780137542970

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Identify the base and write the balanced chemical equation for its reaction with water. For dimethylamine, \((CH_3)_2NH\), the reaction with water is: \((CH_3)_2NH + H_2O \rightleftharpoons (CH_3)_2NH_2^+ + OH^-\).

Write the expression for the base dissociation constant \(K_b\) for dimethylamine. The \(K_b\) expression is: \(K_b = \frac{[(CH_3)_2NH_2^+][OH^-]}{[(CH_3)_2NH]}\).

For the carbonate ion \(CO_3^{2-}\), write the balanced chemical equation for its reaction with water: \(CO_3^{2-} + H_2O \rightleftharpoons HCO_3^- + OH^-\).

Write the \(K_b\) expression for the carbonate ion. The \(K_b\) expression is: \(K_b = \frac{[HCO_3^-][OH^-]}{[CO_3^{2-}]}\).

For the formate ion \(CHO_2^-\), write the balanced chemical equation for its reaction with water: \(CHO_2^- + H_2O \rightleftharpoons HCHO_2 + OH^-\). Then, write the \(K_b\) expression: \(K_b = \frac{[HCHO_2][OH^-]}{[CHO_2^-]}\).

Key Concepts

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

Base Ionization

Base ionization refers to the process by which a base reacts with water to produce hydroxide ions (OH-) and the corresponding conjugate acid. For example, when dimethylamine reacts with water, it accepts a proton (H+) from water, leading to the formation of its conjugate acid and hydroxide ions. Understanding this process is crucial for writing the chemical equations and Kb expressions.

Equilibrium Constant (Kb)

The base dissociation constant (Kb) quantifies the strength of a base in solution. It is defined as the ratio of the concentration of the products (conjugate acid and hydroxide ions) to the concentration of the reactants (the base) at equilibrium. The Kb expression is essential for calculating the extent of ionization of the base in water and is derived from the balanced chemical equation.

Conjugate Acid-Base Pairs

Conjugate acid-base pairs are related species that differ by the presence of a proton (H+). When a base accepts a proton, it forms its conjugate acid. Recognizing these pairs is vital for writing the correct chemical equations and Kb expressions, as it helps identify the products of the reaction and their respective concentrations in the equilibrium expression.

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