C3.3 - CHEMICAL REACTIONS

• what is oxidation in terms of oxygen?

  oxygen is add to an element/compound
• what is reduction in terms of oxygen?

  oxygen is removed
• what is a redox reaction?

  oxidation and reduction happen at the same time
• what has been oxidised and reduced?

  ZnO + C = Zn + CO

  carbon atom has been oxidised

  zinc oxide has been reduced
• an oxidising agent gives oxygen to another substance. e.g. zinc oxide
• oxidation is loss of electrons.

  reduction is the gain of electrons
• what happens when acids are added to water?

  form positively charged hydrogen ions (H+)
• what happens when alkalis are added to water?

  form negative hydroxide ions (OH-)
• pH indicator brown/red?

  acidic
• pH indicater blue/purple?

  alkaline
• pH indicator green?

  neutral
• neutralisation word equation?

  acid + base = salt + water
• overall ionic equation for neutralisation?

  H+ + OH- = H2O
• sulfuric acid?

  H2SO4
• nitric acid?

  HNO3
• acid with metal carbonate word equation?

  acid + base = salt + water + carbon dioxide
• acid and metal word equation?

  acid + metal -> salt + hydrogen gas
• when added to water, acids ionise/dissaciate to product H+ ions.

  • completely dissociate = high concentration of H+ ions = very low pH
  • partially ionise = low concentration of H+ = higher pH (but still under 7)
• • The ⇌ symbol indicates that the process is reversible, as the products can react together forming the original reactants
• concentrated and dilute acids

  first fill in concentration level and then strength

  A) concentrated

  B) weak

  C) concentrated

  D) strong

  E) dilute

  F) weak

  G) dilute

  H) strong

  
• • The pH scale is logarithmic, meaning that each change of 1 on the scale represents a change in concentration by a factor of 10
• Titration curves demonstrating the effect of changing pH when a base is added to an acid and vice versa 

  A) base

  B) acid