Reducing Agents

  • Commonly used reducing agents include;
  • KI-iodides;
  • Sodium thiosulphate -thiosulphate ions

Potassium Iodide, KI

  • I(aq) is oxidized to I2(aq)-brown or I2(s)-black ppt


Observations and deductions when KI is added to various test reagents
Observations Deductions Notes
Pale solution to brown ppt plus few white ppt Cu2+ present Cu2+ is reduced to Cu1+
white ppt is CuI(s)
a bright yellow ppt soluble in excess KI to give colourless sln Pb2+ present yellow PbI2 dissolves in excess KI bcz a complex PbI42- is formed
A dark brown sln from pale red brown sln; black ppt forms slowly Fe3+ Fe(iii) to Fe(ii)
purple sln to faint pink sln Mn2+ present Mn7+ to Mn2+

Hydrogen Peroxide

  • it can act as a reducing agent in some reactions
  • oxygen gas is liberated, you should prepare to test for oxygen.
  • examples include;
  • Acidified hydrogen peroxide reduces Mn(7+) to Mn(2+)
  • pH change may affect the behaviour of hydrogen peroxide in redox reactions eg;
  • in acidic medium: Mn(7+) is reduced to Mn(2+)
  • in alkaline medium: Mn(2+) is oxidized to Mn(4+) -dark brown ppt


Oxidizing Agents

Leave a Reply

Your email address will not be published. Required fields are marked *