MORE CHEM ACIDS

• Acid


  A substance containing hydrogen which can be replaced directly or indirectly by a metal to form a salt
• Acid


  A proton donor
• Acids contain hydrogen and can give ('donate') their H+ ions or protons to other reactants
• Aqueous solutions of acids have the following properties: sour taste, corrosive, change blue litmus to red, pH less than 7, are electrolytes
• Acid reacting in aqueous solution

  H+ ions in the acid are replaced by metal or ammonium ions to form a salt
• Acid reacting with reactive metals

  Form a salt and hydrogen gas
• Acid reacting with bases

  Form a salt and water
• Acid reacting with metal carbonates and hydrogencarbonates

  Form a salt, carbon dioxide and water
• Classifications of acids


  • Inorganic or organic
  • Strong or weak
  • Concentrated and dilute
  • Based on basicity
• Inorganic acids


  Derived from inorganic compounds, form hydrogen ions when dissolved in water
• Organic acids


  Derived from living organisms, consist mainly of carbon, hydrogen and oxygen, dissolve in water to liberate H+ ions from their carboxyl group
• Strong acids


  Totally dissociate in water to form their ions
• Weak acids


  Only partially dissociate into their ions in aqueous solution
• Dilute acids


  Have a low concentration of acid in aqueous solution
• Concentrated acids


  Have a high concentration of acid and a small quantity of water
• Basicity


  The number of H+ ions produced per molecule of acid when the acid dissolves in water
• Monobasic acids


  Produce one H+ ion per molecule
• Dibasic acids


  Produce two H+ ions per molecule
• Tribasic acids


  Produce three H+ ions per molecule
• Acid anhydrides


  Compounds that react with water to form an acid
• Acid anhydrides


  • Carbon dioxide (CO2)
  • Sulfur dioxide (SO2)
  • Sulfur trioxide (SO3)
  • Nitrogen dioxide (NO2)
• Acids in living organisms and everyday activities

  • Ascorbic acid (vitamin C)
  • Citric acid
  • Methanoic acid
  • Lactic acid
  • Ethanoic acid
• Acids have many uses in industry such as manufacturing fertilisers, detergents, car batteries, and as rust removers
• Acid


  A substance which produces hydrogen ions when dissolved in water

  
• Base


  A proton acceptor, or a substance which dissolves in water to produce hydroxide ions (OH- (aq))

  
• Alkali


  A soluble base
• Properties of aqueous acids

  • Sour taste
  • Turns moist blue litmus paper red
  • Electrolytes
  • Corrosive
  • pH < 7
• Strength of acids


  Indicates the extent to which a substance dissociates in water
• Strong acid


  Completely dissociates/ionises into ions when dissolved in water
• Dissociation of strong acids

  1. H Cl(aq) → H+(aq) + Cl-(aq)

  2. H NO3(aq) → H+(aq) + NO3-(aq)

  3. H2 SO4(aq) → 2 H+(aq) + SO42-(aq)

  
• Weak acid


  Only partially dissociates/ionises into ions when dissolved in water
• Dissociation of weak acids

  1. CH3COO H(aq) ⇌ H+(aq) + CH3COO-(aq)

  2. HCOO H(aq) ⇌ H+(aq) + HCOO-(aq)

  3. H2SO3(aq) ⇌ H+(aq) + HSO3-(aq)

  4. H2CO3(aq) ⇌ H+(aq) + HCO3-(aq)
• Examples of strong and weak acids

  • Strong acids: HCl, H2SO4, HNO3
  • Weak acids: CH3COOH, H2SO3, HNO2
• Basicity (or proticity) of acids

  The number of moles of replaceable H+ ions it contains per mole of acid
• Types of acids by basicity

  • Monobasic acids
  • Dibasic acids
  • Tribasic acids
• A neutralization reaction occurs when an acid reacts with a base to form a salt and water only
• Strong alkali


  Completely dissociates into ions when dissolved in water
• Dissociation of strong alkalis

  1. KOH (aq) → K+(aq) + OH-(aq)

  2. NaOH (aq) → Na+(aq) + OH-(aq)

  3. Ca(OH)2 (aq) → Ca2+(aq) + 2 OH-(aq)

  
• Weak alkali


  Only partially dissociates into ions when dissolved in water
• Dissociation of weak alkali

  NH3 (g) + H2O (l) ⇌ NH4+(aq) + OH-(aq)