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Acids and Bases

A series of free High School Chemistry Video Lessons and solutions.

In these lessons, we will learn

  • Acid and Base Properties
  • Strength of Acids and Bases
  • Neutralization and Salts
  • Buffered Solutions
  • pH and pOH

Acid and Base Properties
The Arrhenius definition of acids and bases only applies to aqueous solutions. An acid is a substance that ionizes in aqueous solutions to form hydrogen ions while a base is a substance that accepts hydrogen ions in aqueous solutions, producing hydroxide ions. The Bronsted-Lowery definitions of states that acids donates protons, while bases accept protons. Acid and base properties are important, regardless of what definition we use.
The properties of acids and bases.

What are Acids and Bases?

This introduction to acids and bases discusses their general properties and explains the Arrhenius definitions for acids and bases.
Strength of Acids and Bases
The strength of acids and bases depend on how much an acid or base ionizes in solution. A strong acid or base completely ionizes in solution. In a neutralization reaction, an acid and a base react to produce a salt. A salt is an ionic compound whose cation comes from a base and whose anion comes from an acid.

This lesson discusses the difference between strong and weak acids and bases, and relates it to the acid dissociation constant (Ka) and the base dissociation constant (Kb).

Strong vs. Weak - Acids and Bases; pH Calculations
Definitions of strong and weak acids/bases;
pH calculations for strong and weak acids.
Salts are ionic compounds whose cations comes from bases and whose anions come from an acids. They are formed through neutralization reactions in which the reactants are an acid and a base and the products are salt and water.
How neutralization reactions produce salts.

Neutralization and Salts
This lesson describes acid base neutralization and the formation of salts from neutralization reactions. We show how conjugate rules can be used to determine acidity or basicity of salts.
Buffered Solutions
Buffered solutions are solutions that are “buffered” by the presence of weak acid and a conjugate base. Buffered solutions resist change in pH when acids or bases is added to it by reacting with any added hydrogen or hydroxide ions so that they do not accumulate. Therefore, buffered solutions are used to keep pH at a constant value.
How acids and bases are used in buffered solutions.

Buffer solutions are designed to maintain the pH of solution by reacting with small amounts of added acid or base. We show how to calculate the pH of a buffer solution using the Henderson-Hasselbalch equation, and how to select an appropriate acid-base combination to prepare a buffer solution at any desired pH.
pH and pOH
pH and pOH denote the negative log of the concentration of hydrogen or hydroxide ions. High pH means that a solution is basic while high pOH means that a solution is acidic. Neutral solutions have pH and pOH of 7

This lesson introduces the pH scale and discusses the relationship between pH, [H+], [OH-] and pOH.

How pH and pOH represent the concentration.

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