Problem: Balance the following oxidation-reduction reaction: K(s) + H2O (l) → KOH (aq) + H2(g)

FREE Expert Solution

Recall the mnemonics LEO GER.

Lose               Gain

Electron         Electrons

Oxidation       Reduction


  • Oxidation States:
    • elements = 0
    • ions = charge 


Determine O.S.:

  • K (s) = 0 (element) 
  • H2O:
    • H = +1 (w/ nonmetals, not metal hydride)
    • O = -2 (in most cpds, not peroxide/superoxide)
  • KOH (aq) → K+ + OH-
    • K = +1
    • OH- : sum of O.S. in ions = charge of ion
      • H = +1
      • O = -2 
  • H= 0 (diatomic element)


Determine change in O.S.:

  • K: 0 to + 1 → increased/more positive → lost e→ oxidation
  • H: +1 to 0 → decreased → gained e-  → reduction
  • O: no change
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Problem Details

Balance the following oxidation-reduction reaction: K(s) + H2O (l) → KOH (aq) + H2(g)

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