Worked example: Finding the percent ionization of a weak acid | AP Chemistry | Khan Academy

TL;DR

This video explains how to calculate the pH and percent ionization of a 0.20 Molar solution of acetic acid using an ICE table and the 5% rule.

Transcript

• [Instructor] Let's say we have a 0.20 Molar aqueous solution of acidic acid. And our goal is to calculate the pH and the percent ionization. The Ka value for acidic acid is equal to 1.8 times 10 to the negative fifth at 25 degrees Celsius. First, we need to write out the balanced equation showing the ionization of acidic acid. So acidic acid reac... Read More

Key Insights

• 🥶 An ICE table is a useful tool for determining equilibrium concentrations and calculating pH and percent ionization of weak acid solutions.
• 😑 The equilibrium constant expression for the ionization of an acid is derived from the balanced equation, considering the stoichiometry of reactants and products.
• 🤝 Approximations can be used to simplify calculations when dealing with weak acids and small equilibrium concentrations.

Summary & Key Takeaways

• The video demonstrates the process of setting up an ICE table to determine the equilibrium concentration of hydronium ion, pH, and percent ionization for a weak acid (acetic acid) solution.

• The ICE table is used to track the initial concentration, change in concentration, and equilibrium concentration of the reactants and products in the acid's ionization reaction.

• The video explains how to set up the equilibrium constant expression using the balanced equation and how to use an approximation to solve for the equilibrium concentration of hydronium ions, avoiding the use of a quadratic equation.