Acids & Bases

• Acid

  A substance that dissociates/ionises in water to produce H+ ions (hydrogen)
• Acid in organic solvents

  No dissociation/ionization to give H+ ions (hydrogen)
• Strong acids

  Fully dissociates in water to form high concentration of H+ ions
• Weak acids

  Partially dissociates in water to form lower concentration of H+ ions
• Examples of strong acids

  • HCl (hydrochloride acid)
  • HNO3 (nitric acid)
  • H2SO4 (sulfuric acid)
• Examples of weak acids

  • H3PO4 (phosphoric acid)
  • CH3COOH (ethanoic acid)
• Properties of acids

  • sour
  • produce ions when dissolved in water (conduct electricity)
  • turn blue litmus paper red
• Salts

  Ionic compounds, compounds that contain an element that is a metal.
• Acid reactions

  Acid + reactive metals -> salt + hydrogen gas

  Acid + metals oxide/hydroxide -> salt + water

  Acid + metal carbonate -> salt + carbon dioxide + water
• Test for hydrogen gas

  Use lighted splint

  Positive: extinguish with a ‘pop’ sound
• Metal reactivity list

  Potassium (K)

  Sodium (Na)

  Calcium (Ca)

  Magnesium (Mg)

  Aluminium (Al)

  Zinc (Zn)

  Iron (Fe)

  Lead (Pb)

  Copper (Cu)

  Silver (Ag)

  Gold (Au)
• Lead + hydrochloride/sulfuric acid

  Reaction stops halfway. initial reaction produces an insoluble layer of Lead(II) chloride/sulfate, preventing further reaction
• Test for carbon dioxide

  Bubble gas into limewater (calcium hydroxide), white precipitate (calcium carbonate) formed
• Complete reaction of acid + reactive metals

  • effervescence observed
  • metal dissolves
• Complete reaction of acid + metal oxide/hydroxide

  • solid base dissolves
  • warm to touch
• Complete reaction of acid + metal carbonate

  • effervescence observed
  • metal carbonate dissolves
• Basicity of acids

  no. of hydrogen ions produced by ionisation of one molecule of acid when dissolved in water
• Base

  Metal oxide/hydroxide that contain oxide(O2-)ions or hydrogen(OH-) ions. Mostly insoluble
• Alkali

  Soluble base that dissociates in water to produce hydroxide (OH-) ions