Acids and redox

• All acids contain

  Hydrogen
• When dissolved in water an acid releases

  Hydrogen ions as protons, H+
• A strong acid releases all its hydrogen atoms into solution and completely dissociates in aqueous solution
• A weak acid only releases a small proportion of its avaliable hydrogen atoms into solution so only partialy dissociates in aqueous solution
• Bases

  A base neutralises an acid to form a salt. Bases include:

  • Alkalis
  • Metal oxides
  • Metal hydroxides
  • Metal carbonates
  • Ammonia
• Alkali

  A base that releases Hydroxide ions OH- into the solution
• Acid + alkali

  Salt + water
• Acid + carbonate

  Salt + water + carbon dioxide
• Oxidation number for elements

  Always 0 in a pure element eg. H2, Na
• Special cases of oxidation numbers

  • H in metal hydrides = -1
  • O in peroxides = -1
  • O bonded to F = +2
• Roman numerals

  Name compounds of elements that form ions with different charges eg:

  Iron(II) represents Fe2+ so its oxidation number is +2
• Reduction is

  The gain of electrons
• Oxidation is

  The loss of electrons
• Redox reaction of acids

  Metal + acid = salt + hydrogen