redox reaction

> Question - My students and I came across this and were stumped. >Oxidation is always accompanied by reduction - so I was taught. >These reactions appear to only have oxidation, where is the reduction? >These steps are from the Ostwald process for producing HNO3 > 1) 4NH3 + 5O2 ---> 4NO + 6H2O > >2) 2NO + O2 ---> 2 NO2 > >3)3NO2 + H2O ---> 2HNO3 + NO > >Steps 1 and 2 show oxidation of nitrogen 3- to 2+ and 2+ to 4+ >Step 3 shows 4+ to 5+ and 4+ to 2+, a normal redox reaction----------------------------------------------------------------------For the first reaction, the oxidation numbers are: -3 +1 0 +2 -2 +1 -2 4 N H_3 + 5 O_2 --> 4 N O + 6 H_2 ONitrogen is oxidized from -3 to +2, and oxygen is reduced from 0 to -2.The half reactions would be, following the old mnemonic ``LEO the liongoes GER'':4 NH_3 ---> 4 N(2+) + 12 H(+) + 20 e- (LEO -> Loss of Electrons = Oxidation)5 O_2 + 20 e- ---> 10 O(2-) (GER -> Gain of Electrons = Reduction)Probably you can carry on from here.Grayce=============================================You overlooked the oxygens. In steps 1 and 2, oxygen is reduced.