 So here are the rules for balancing a redox equation. We're doing this in acidic conditions So you need to write skeleton equations of the reduction and oxidation half reactions balance for everything other than hydrogen and oxygen Balance for oxygen by adding water where required balance for hydrogen by adding hydrogen ions where required Balance for charge by adding electrons Then you need to get the same number of electrons in the reduction and oxidation half equations Then you add together and cancel out anything on both sides of the arrow and then at the end you check So let's do an example So we're going to balance this equation here So the first step we need to write the oxidation or reduction half equations. So I'm going to start with technician So technician goes to TE03 to minus And in O3 minus goes to N2O4 All right, so we've done the half equations now What I need to do is our balance for everything other than oxygen and hydrogen So if we look we've got one technician one technician so the top equation is okay Bottom one we've got two nitrogens on the left and only one on the two nitrogens on the right and one on the left So I need to double my number of nitrate ions Next step is we need to balance for oxygen by adding water molecules where required So we now first equation here. We've got Three water three oxygen molecules on the right-hand side. So you need to add three water Molecules to the left-hand side In our bottom one, we've got two two times three So we've got six oxygens on the left-hand side and only four on the right-hand side. So I need add Two water molecules on the right Next step is we need to balance for hydrogen by adding hydrogen ions where required So we've got six hydrogens on the left-hand side here and on the right So I need to add six hydrogen ions to the right now bottom one. We've got four hydrogens On the right-hand side. So we need to add four hydrogen ions to the left Next step is we need to balance for charge by adding electrons. So if we look at our top equation here We've got no charge anywhere. So our charge is zero on the left-hand side if we look at our right-hand side Got minus two here and six H pluses here So we've got plus six minus two so a total charge is plus four So to get the charges the same on both sides I need to add four electrons to the right-hand side of our top equation look at our bottom equation I've got a charge of zero on the right-hand side then on the left-hand side. I've got Two negatives there and plus four so my total charge on this side So minus two plus four is plus two. So that means I need to add two electrons To the left-hand side of the bottom equation next step is we need to Get the number of electrons the same. So if I look at the top I've got four electrons at the top and only two down the bottom So I need times everything down the bottom by two. So now I've got four electrons plus four Nitrate ions plus eight hydrogen ions Going to two into four plus four Water molecules, so I'm just using it as if it's a mathematical equation I'm multiplying everything down the bottom by two Next step we need to treat these equations as their mathematical equations and cancel out things that are on both sides the arrow And then add them together So if we have a look at our equations here You should be able to get rid of the electrons if you can't get rid of the electrons you've done something wrong We've got three water molecules on the left of the arrow at the top before down the bottom So you can get rid of all three up here and we've got one water molecule left on the right hand side down the bottom We can also get rid of our hydrogen ions or some of them So we've got six hydrogen ions here eight down the bottom. So that leaves me with two hydrogen ions And now we write out our what we have left over. So we've got technician plus four Nitrate Plus two hydrogen ions goes to Teo three two minus plus into Oh four plus each two oh Next step is we need to check to make sure we've got the same on both sides of the equation So first thing we're going to do is check for charge So I've got minus four down here and plus two over here So minus four plus two is minus two so the total charge of minus two On our right hand side over here. We've got minus two so our charges minus two on both sides So that's a good now a good thing to see Next we need to check that we've got the right number of all the atoms there So we've got one technician one technician four nitrogen For the two there we go. So I've got that too. So two times two. So we've got four nitrogen I've got four times three. So 12 oxygens. I've got eight plus three is 11 plus one is 12 oxygens Two hydrogen is two hydrogeners. So everything's balanced there. So that one is done So we've done the redox equation for those two and added them together