Acids and Bases and Chemical Equilibrium: Study Notes

Acids and Bases and Chemical Equilibrium

Introduction

This chapter introduces the fundamental concepts of acids, bases, and their behavior in aqueous solutions, including their classification, naming, properties, and the concept of chemical equilibrium. Understanding these concepts is essential for further study in general, organic, and biological chemistry.

Acids

Arrhenius Acids

• Definition: An Arrhenius acid is a substance that produces hydrogen ions (H+) when dissolved in water.

• General Reaction: $\mathrm{HCl}(g) \xrightarrow{H_2O} \mathrm{H}^+(aq) + \mathrm{Cl}^-(aq)$

• Properties:

  • Produce H+ in water (often written as H3O+, the hydronium ion).

  • Are electrolytes because they conduct electricity in solution.

  • Have a sour taste.

  • Turn blue litmus paper red.

  • Can corrode some metals.

Naming Acids

• Binary Acids: Acids composed of hydrogen and a nonmetal are named with the prefix hydro- and the suffix -ic acid.

  • Example: HCl is hydrochloric acid.

• Oxoacids: Acids containing hydrogen and a polyatomic ion (usually containing oxygen) are named by modifying the name of the polyatomic ion:

  • If the ion ends in -ate, the acid ends in -ic acid.

  • If the ion ends in -ite, the acid ends in -ous acid.

  • Examples:

    • ClO3- (chlorate) → HClO3 is chloric acid

    • ClO2- (chlorite) → HClO2 is chlorous acid

Table: Names of Common Acids and Their Anions

Name of Acid	Anion	Name of Anion
Hydrochloric acid	Cl-	Chloride
Hydrobromic acid	Br-	Bromide
Hydroiodic acid	I-	Iodide
Hydrocyanic acid	CN-	Cyanide
Nitric acid	NO3-	Nitrate
Nitrous acid	NO2-	Nitrite
Sulfuric acid	SO42-	Sulfate
Sulfurous acid	SO32-	Sulfite
Carbonic acid	CO32-	Carbonate
Acetic acid	C2H3O2-	Acetate
Phosphoric acid	PO43-	Phosphate
Phosphorous acid	PO33-	Phosphite
Chloric acid	ClO3-	Chlorate
Chlorous acid	ClO2-	Chlorite

Bases

Arrhenius Bases

• Definition: An Arrhenius base is a substance that produces hydroxide ions (OH-) when dissolved in water.

• General Reaction: $\mathrm{NaOH}(s) \xrightarrow{H_2O} \mathrm{Na}^+(aq) + \mathrm{OH}^-(aq)$

• Properties:

  • Taste bitter or chalky.

  • Are electrolytes because they conduct electricity in solution.

  • Feel soapy and slippery.

  • Turn red litmus paper blue.

  • Turn phenolphthalein indicator pink.

Naming Bases

• Most common Arrhenius bases are named as hydroxides of metals.

• Examples:

  • NaOH: sodium hydroxide

  • KOH: potassium hydroxide

  • Ba(OH)2: barium hydroxide

  • Al(OH)3: aluminum hydroxide

Summary Table: Properties of Acids and Bases

Property	Acids	Bases
Arrhenius definition	Produce H+	Produce OH-
Electrolyte?	Yes	Yes
Taste	Sour	Bitter, chalky
Touch	May sting	Soapy, slippery
Litmus test	Blue to red	Red to blue
Phenolphthalein	Colorless	Pink
Neutralization	Neutralize bases	Neutralize acids

Example: Naming Acids and Bases

• HBr: Hydrobromic acid (binary acid, hydrogen + bromine)

• H2CO3: Carbonic acid (oxoacid, polyatomic ion carbonate)

• HNO2: Nitrous acid (oxoacid, polyatomic ion nitrite)

Additional info: The above content is based on the first several slides and text, which focus on the Arrhenius definitions, naming, and properties of acids and bases. Further sections would cover Bronsted-Lowry theory, conjugate acid-base pairs, strong/weak acids and bases, equilibrium, pH, and buffer systems.