(35) (7th of 19 Chapters) Acids, Bases, Oxides & Ionic Equations - GCE O Level Chemistry Lecture

Solubility of Compounds

• Compounds containing sodium, potassium, or ammonium are soluble in water.

Acids and Bases

• Definitions:

  • Acids: Substances that dissociate in water to produce hydrogen ions (H⁺).

  • Bases: Oxides or hydroxides of metals that react with acids to form salt and water.

Types of Acids

• Basicity Types:

  • Monobasic: Donates one hydrogen ion.

  • Dibasic: Donates two hydrogen ions.

  • Tribasic: Donates three hydrogen ions.

• Strength: Refers to the degree of dissociation in water.

• Concentration: Refers to the amount of acid or base in a given volume of solution.

Indicators and pH Scale

• Indicators: Tools to measure acidity and basicity.

  • Example: Litmus paper changes color in acids and bases.

• pH Scale: Ranges from 0 to 14.

  • Lower values indicate acidity.

  • Higher values indicate basicity.

Reactions of Acids and Bases

• Neutralization Reactions:

  • An acid reacts with a base to produce salt and water.

  • Example: [ \text{HCl (aq) + NaOH (aq) → NaCl (aq) + H}_2\text{O (l)} ]

• Ionic Equations: Represent the actual species involved in a chemical reaction.

Amphoteric Oxides

• Definition: Can react with both acids and bases.

• Example: Aluminum oxide.

  • Reacts with hydrochloric acid (behaves like a basic oxide) to produce aluminum chloride and water.

  • Reacts with sodium hydroxide (behaves like an acidic oxide) to produce sodium aluminate and water.

Types of Oxides

• Acidic Oxides: React with bases to form salt and water.

• Basic Oxides: React with acids to form salt and water.

• Amphoteric Oxides: React with both acids and bases.

  • Example: Zinc oxide, Lead(II) oxide, Aluminum oxide.

• Neutral Oxides: Do not exhibit acidic or basic properties; do not react with acids or bases.

  • Example: Water, Carbon monoxide, Nitrogen monoxide.

Writing Ionic Equations

• Steps to Write Ionic Equations:

  1. Write the balanced chemical equation.

  2. Dissociate soluble ionic compounds into their ions.

  3. Cancel out spectator ions (ions that appear on both sides of the equation).

  4. Write the net ionic equation showing the species that participate in the reaction.

Example Ionic Equations

1. Neutralization Process:

   • Reaction: [ \text{NaOH (aq) + HCl (aq) → NaCl (aq) + H}_2\text{O (l)} ]

   • Ionized: [ \text{Na}^+ (aq) + \text{OH}^- (aq) + \text{H}^+ (aq) + \text{Cl}^- (aq) → \text{Na}^+ (aq) + \text{Cl}^- (aq) + H_2O (l) ]

   • Net Ionic Equation: [ \text{H}^+ (aq) + \text{OH}^- (aq) → H_2O (l) ]

Summary of Oxides and Ionic Equations

• Three Types of Oxides:

  • Acidic, Basic, Amphoteric.

• Neutral Oxides: Do not react with acids or bases.

• Neutralization Reaction: Results in salt and water only.

Conclusion

• Understanding acids, bases, and their reactions is fundamental in chemistry, relevant in various processes and applications.