General Chemistry 2

• Properties of Acids

  1. Taste sour.
  2. Turn blue litmus paper red - this is an easy test for acid.
  3. Soluble in water.
  4. React with active metals to produce hydrogen gas.
  5. If concentrated they can be corrosive.
  6. Contains hydrogen ions.
• Properties of Bases

  1. Taste bitter.
  2. Turn red litmus paper to blue.
  3. Feel slippery or soapy.
  4. React with acids to form salt and water.
• Properties of Salts

  1. Mostly solids.
  2. Generally soluble in water.
  3. Found as crystals or white crystalline powder.
  4. Salty taste.
• It is a measure of the molar concentration of hydrogen ions in the solution.

  PH of a solution
• It is a measure of the acidity or basicity of the solution.

  Ph of a solution
• Are chemicals used to determine whether a solution is acidic, neutral, or alkaline.

  Acid-Base Indicators
• Litmus Paper

  PH Paper

  Phenolphthalein

  Red Cabbage Juice


  Examples of Acid-Base Indicators
• Examples of Acids

  1. HCL
  2. H2SO4
  3. Citric Acid (C6H8O7)
• Examples of bases.

  1. NaOH
  2. CaOH
  3. NH4OH
• Examples of salts

  1. NaCl
  2. CaCO3
• Neutralization of acids.


  Neutralizes bases.
• Neutralization of bases.


  Neutralises acids.
• Neutralisation of salts.


  Formed on neutralisation.
• Identification of acids.

  Contain replaceable hydrogen.
• Identification of bases.

  Metal oxides, metal hydroxides, ammonium hydroxide.
• Identification of salts.

  Cation (not H+) and anion (not O2- or OH-).
• Solubility in water of acids.

  Soluble.
• Solubility of bases.

  Few bases are soluble (alkali).
• Solubility of salts.

  Two types: soluble and insoluble
• Indicator tests for acids.

  Blue litmus turns red; phenolphthalein remains colorless.
• Indicator tests for bases.

  Red litmus paper turns blue; phenoltphthalein turns pink.
• Indicator tests for salts.

  Litmus no change; phenolpthalein remains colorless.
• To cancel the effect of.

  It is a chemical reaction in which acid and a base react quantitatively with each other.

  Neutralization
• Acid + Base = Salt + Water
• All acids contain hydrogen.
• Bases are metal oxides, metal hydroxides, and NH4OH.
• • Most bases are insoluble in water.
  • Soluble bases are called alkalis.
  • Sodium Hydroxide
  • Potassium Hydroxide
  • Ammonium Hydroxide
  • Calcium Hydroxide - Low Solubility
  • Magnesium Hydroxide - Partially Soluble
• 1. Soluble - Sodium Chloride
  2. Insoluble - Calcium Carbonate


  Two types of salts.
• The acid and base needed to form the salt ammonium nitrate.

  Ammonia (HNO3) + Nitric Acid (NH3) = Ammonium Nitrate (NH4NO)
• The name of acid present in vinegar.

  Acetic Acid (CH3COOH/CH3CO2H/C2H4O2/HC2H3O2)
• The name of acid present in milk.

  Lactic Acid (C3H6O3)
• The name of acid present in tomatoes.

  Citric Acid (C6H8O7), Malic Acid (C4H6O5), Ascorbic Acid (C6H8O6), Oxalic Acid (C2H2O4)
• The name of acid present in citrus fruits.

  Citric Acid (C6H8O7)
• The name of the base present in bar soap.

  Sodium Hydroxide (NaOH)
• The name of the base present in liquid soap.

  Potassium Hydroxide (KOH)
• The Arrhenius Theory

  • In 1680, Robert Boyle noted that acids:

  1. Dissolve many substances.
  2. Change the colors of some natural dyes.
  3. Lose their characteristic properties when mixed with alkalis.

  • In 1814, J.Gay-Lussac concluded that acids neutralise bases.
  • In 1884, Svante Arrhenius presented his theory of electronic dissociation, which resulted in the Arrhenius Theory of acid-base reactions.

  1. In his view, an acid is a substance that contains hydrogen and produces H+ in aqueous solution.
  2. A base is a substance that contains OH (Hydroxyl) group and produces Hydroxide Ions OH- in aqueous solution.
• Neutralisation - Is defined as the combination of H+ ions with OH- ions to form H2O.

  • The Bronsted-Lowry Theory
  • In 1923, J.N. Bronsted (1879-1947) and T.M. Lowry (1874-1936) independently presented logical extension of the arrhenius theory.
  • An acid is defined as a proton donor (H+).
  • A base is defined as a proton acceptor.

  Acid-base reaction is the transfer of a proton from an acid to a base.
• The complete ionisation of HCL, a strong acid in water, is an acid-base reaction in which water acts as a base or proton acceptor.

  Step 1: HCL = (H+) + (CL-) (Arrhenius Description)

  Step 2: H2O + (H+) = H3O+

  Overall: H2O + HCl = H3O + Cl- (Bronsted-Lowry Description)
• We can describe Bronsted-Lowry acid-base reactions in terms of conjugate acid-base pairs.

  • H2O + HF = H3O + F
  • H2O + HCL = H3O + Cl
  • NH3 + H2O = NH4 + OH

  The stronger the acid, the weaker its conjugate base. The weaker the acid, the stronger is its conjugate base.
• The equation for the ionisation of HNO3 in water.

  HNO₃(aq) + H₂O(l) → NO₃⁻(aq) + H₃O⁺(aq).