4 - Acids and Redox

• acid - a compound that releases H+ ions in aqueous solution
• strong acid - a compound that completely dissociates in aqueous solution to form H+ ions
• standard solution - a solution of a known concentration
• alkali - a base that releases OH- ions when dissolved in aqueous solution
• percentage uncertainty = (uncertainty / actual value) x100

  • make sure that if two values were measured for the actual value (ie titre) than it would be (0.05 x 2) for example
• how could the effects of percentage uncertainty be reduced on a burette?

  • use a larger volume of the chemical
  • in order to obtain a larger titre reading
• a volumetric flask is used to measure the volume of a solution accurately
• base - neutralises an acid to form a salt
• acid + alkali -> salt + water
• acid + metal oxide -> salt + water
• acid + metal carbonate -> salt + water + carbon dioxide
• acid + metal -> salt + hydrogen
• 4 reactions with acids

  1. acid + metal
  2. acid + metal oxide
  3. acid + metal carbonate
  4. acid + metal hydroxide
• acid + metal hydroxide -> salt + water
• disproportionation reaction - a reaction where an element is both oxidised and reduced
• order of priority for assigning oxidation numbers

  1. group 1 -> +1
  2. group 2 -> +2
  3. F -> -1
  4. H -> +1 (except metal hydrides -> -1)
  5. O -> -2 (except peroxides -> -1 / OF2 -> +2)
  6. Cl -> -1 (except when with O or F)
• complete the table

  A) hydrochloric

  B) sulfuric

  C) nitric

  D) ethanoic

  
• complete the table

  A) HCl

  B) H2SO4

  C) HNO3

  D) CH3COOH

  
• acids have a pH < 7
• bases have a pH > 7
• acids all contain H in their formulae
• complete the equation

  A) H+(aq)

  B) -

  
• ethanoic acid is a weak acid
• hydrochloric acid is a strong acid
• sulfuric acid is a strong acid
• nitric acid is a strong acid
• complete the diagram

  A) CH3COO-

  B) ethanoate ion

  C) incomplete

  
• weak acid - a compound only partially dissociates in aqueous solution to form H+ ions
• sulfuric acid is a strong acid but it dissociates in 2 steps
• sulfuric acid dissociation

  complete the steps

  A) H+

  B) weak

  C) reversible reaction

  D) 2-

  
• common formula for bases

  (use M for 1+ and A for 2+)

  A) ACO3

  B) MOH

  C) AO

  
• three main types of bases

  • metal oxides
  • metal carbonates
  • alkalis
• ammonia is an alkali
• strong alkali - the OH- is included in the alkali formula
• weak alkali - reacts with water to form OH- ions
• complete the equation

  A) H2O(l)

  B) OH-(aq)

  
• ammonia is a weak alkali
• sodium hydroxide is a strong alkali
• ionic equation - an equation that only shows the ions that take part in the reaction (excludes spectator ions)
• what is the ionic equation for the reaction between acids and alkalis, include state symbols

  A) H+(aq)

  B) OH-(aq)

  C) H2O(l)