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Introduction to Acids and Bases

• Importance of understanding acids and bases in chemistry.

Acids and Bases Properties

Characteristics of Acids

• Taste: Sour taste.

• Reaction with Indicators: Turn universal indicator red.

• Skin Reaction: Burns human skin;

• Reactivity: Corrosive on metals.

• Ion Dissociation: Dissociates into ions in aqueous solutions, releasing H+ ions.

  • Examples: Lemon juice, Vinegar.

Characteristics of Bases

• Taste: Bitter taste.

• Reaction with Indicators: Turn universal indicator blue.

• Skin Reaction: Feel slippery/soapy on human skin.

• Reactivity: Corrosive on metal solutions.

• Ion Dissociation: Dissociates into ions in aqueous solutions, releasing OH- ions.

  • Examples: Milk of magnesia, Household ammonia.

Fundamental Concepts

Basic Terms and Definitions

• Protons: Represented as H+.

• Hydronium ions (H3O+): H+ attached to water.

• Hydroxide ions (OH-): Represents alkaline nature.

• Molarity (M): Concentration measure in moles per liter.

• Acidic: [H3O+] > [OH-].

• Basic: [H3O+] < [OH-].

• Neutral: [H3O+] = [OH-].

• pH scale: Measures acidity/basidity.

  • pH < 7: Acidic

  • pH > 7: Basic

  • pH = 7: Neutral

Calculating pH

Relationship between pH and Hydronium Concentration

• Formula: pH = −log [H3O+]

• To calculate [H3O+]: [H3O+] = 10^(-pH).

  • Example:

    • Coke: [H3O+] = 0.001 M, pH = -log(10^(-3)) = 3.

    • Orange Juice: [H3O+] = 0.0001 M, pH = -log(10^(-4)) = 4.

Estimating pH Experimentally

• Method: Use acid-base indicators.

• Types of Indicators: Complex organic compounds that change color at different pH levels or universal indicators.

• Example: Red cabbage juice changes color based on acidity or basicity.

pH of Various Solutions

• A solution becomes more acidic as [H3O+] increases, thus decreasing pH. Conversely, as a solution becomes more basic with increased [OH-] or lower [H3O+], the pH value increases.

Water and pH

Pure Water Characteristics

• Generates equal concentrations of H3O+ and OH- ions, resulting in pH = 7.

  • Equation: H2O + H2O ⇄ H3O+ + OH−

• Water in equilibrium helps maintain body conditions.

Identifying Acidic and Basic Solutions

• Acidic Reaction: Excess H3O+ ions (>10^-7 M).

• Basic Reaction: Excess OH- ions (>10^-7 M).

  • Example: In pure water, both ion concentrations equal 1.0×10^−7 M, showing neutrality.

Understanding Acids and Bases

Sources of Acids and Bases

• Binary Acids: Involve two elements, produced by dissolving molecular compounds in water.

• Nonmetal Oxides: React with water to form acids, contributing to acid rain.

  • Example: CO2 + H2O → H2CO3, H2SO4 formation from SO3.

• Basic Oxides: Produce hydroxides when reacting with water.

Properties of Acids and Bases

• Arrhenius Definition:

  • Acids release H+ in water.

  • Bases release OH- in water.

• Brønsted-Lowry Definition:

  • Acids donate H+ ions, bases accept H+ ions.

Strength of Acids and Bases

Differentiating Strengths

• Strong Acids: Completely ionize in solution (100%). Examples: HCl, HNO3, sulfuric acid.

• Weak Acids: Partially ionize. Examples: HF, organic acids.

• Strong Bases: Hydroxides that ionize completely (e.g., NaOH).

• Weak Bases: Form fewer ions in solution, largely remaining undissociated (e.g., NH3).

Neutralization Reactions

• Definition: Acid-base reactions lead to the formation of water and a salt.

  • General equation: HA + BOH → BA + H2O

• Examples:

  • HCl + NaOH → NaCl + H2O.

Titration Concepts

Acid-Base Titration Details

• Used for determining unknown concentrations: Addition of known concentration to unknown until equivalence point.

• Examples involve calculating molarities based on observed titrations.

Buffer Solutions

Overview of Buffers

• Maintain stable pH; consist of a weak acid and its conjugate base or weak base and its conjugate acid.

• pH of buffer solutions is influenced by the concentration ratio of the components.

  • Example: Bicarbonate buffer system (H2CO3/HCO3^-)

Biological Relevance of Acids and Bases

• Understanding acid-base balance is crucial for physiological processes.

• Common buffer systems in the human body include bicarbonates, phosphates, and proteins maintaining pH within optimal ranges.