Acids and redox

• water of crystallisation is the water that is present in the crystals of a mineral
• Rules for assigning oxidation numbers:

  • Simple ions (Na+, Mg2+, O2-) --> the oxidation number is the charge of the ion
  • In elements, the oxidation number is zero (E.g: Mg, Na, Cl)
  • The total of the oxidation numbers = the charge on the species.
  • The more elctronegative element is assumed to have the negative oxidisation number. E.g: F20 --> F will always be -1
• The oxidation number of oxygen in peroxides is -1
• The oxidation number of hydrogen in metal hydrides is -1
• Roman numerals are used to indicate when an element has more than one stable oxidation number
• Oxyanions --> negative ions that have an element along with oxygen
• Redox reactions:

  • Oxidation is addition of oxygen
  • Oxidation is also the loss of electrons
  • Oxidation is an increase in oxidation number
  • Reduction is the removal of oxygen
  • Reduction is also the gain of electrons
  • Reduction is a decrease in oxidation number
• Using roman numerals in naming:

  • Roman numerals shows the oxidation state (oxidation number) of the element, without a sign
  • Iron (II) represents Fe2+ with oxidation number +2
  • Iron (III) represents Fe3+ with oxidation number +3
  • Nitrate (III) = Nitrite (NO2-) --> oxidation number of nitrogen = +3
  • Nitrate (v) = Nitrate (NO3-) --> oxidation number of nitrogen = +5