Calcule la concentración molar de iones OH^-de una disolución 0.075 M de etilamina (C2 H5 NH2)(K

step 1 We are asked to calculate the molar concentration of hydroxide ions in a 0 .075 molar solution o

Calcule la concentración molar de iones OH^-de una...

Calcule la concentración molar de iones $\mathrm{OH}^{-}$de una disolución $0.075 \mathrm{M}$ de etilamina $\left(\mathrm{C}_2 \mathrm{H}_5 \mathrm{NH}_2\right)\left(K_b=6.4 \times\right.$ $10^{-4}$ ). Calcule el $\mathrm{pH}$ de esta disolución.

Key Concepts

Base Ionization Equilibrium

This concept refers to the reaction where a weak base reacts with water to produce its conjugate acid and hydroxide ions. Understanding this equilibrium is essential for determining the concentration of ions produced, which is a foundational topic in acid-base chemistry.

Equilibrium Constant (Kb) and Expression

Kb represents the base ionization constant, which quantifies the strength of a weak base by expressing the ratio of the concentration of products (conjugate acid and hydroxide ions) to the concentration of the unreacted base at equilibrium. The expression Kb = [BH+][OH-] / [B] is key to setting up and solving equilibrium problems involving weak bases.

Approximations in Equilibrium Calculations for Weak Bases

In problems involving weak bases, the degree of ionization is typically small compared to the initial concentration. This allows the approximation that the change in concentration is negligible, thereby simplifying the algebra required to solve for equilibrium concentrations. Recognizing when and how to apply this approximation is crucial for efficiently solving equilibrium problems.

Relationship between [OH-], pOH, and pH

Once the concentration of hydroxide ions ([OH-]) is determined, pOH can be calculated using the formula pOH = -log[OH-]. Since pH and pOH are related by the equation pH = 14 - pOH in aqueous solutions at room temperature, this relationship provides a straightforward method for converting between these measures, which is essential in acid-base chemistry.

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