Learn about Senior Chemistry, Redox 8, in this comprehensive video by bannanaiscool.
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Acidified permanganate ion reacts with iron metal to form iron (H) ion, manganate ion and water. Male Speaker: This equation can now be balanced successfully using oxidation numbers, so if you got an equation you're saying how I balance this thing use oxidation numbers watch this it will actually open the whole world to you. Oxygen is always minus 2, minus 2 times 4 is negative 8, got to keep in negative one so that makes the manganese plus 7, you are with me, hope so, H positive plus one Fe2 Positive plus 2, plus 3, plus 2, oxygen's always minus 2 hydrogen is always plus one, that works out for water giving a total charge of zero. Watch this!! You know this step from one side to the other. Oxygen stays the same. Hydrogen stay the same, they don't under go a change they are not involved in this oxidation reduction reaction, but the Mn goes from plus seven all the way to plus two, if you go for plus seven to plus two you have to gain negatives to become less positive, you know what I'm saying, plus seven to plus two; which means that you've actually gained 5 electrons, this Mn gains 5 electrons going from here to here. Oh well, then that means gaining electrons that's reduction and reduction means that Mn in this compound is the oxidizing agent, Which is undergoing reduction which is gaining electrons okay. What's the iron doing; its going from plus 2, to plus 3, in order to become more positive you have to loose negatives and so this that's a loss of one electrons, hey if you loose one electron what do you want to go in, that's oxidation, and oxidation is meaning that this a reducing agent, reducing agent under going oxidation loosing an electron, oh baby now look at this. This is a redox reaction and I got to pretend that you are adding two half reactions together, look if this wants to gain 5 but this only uses one at a time, what do you usually do when you have like, like half reaction that has forwarded and 1 electron in it, you multiply that what I have 1 by 5. So we take this we multiply it by 5, but that means that this is involved in this half reactions so that its five there you get five electrons you got to put a 5 here, you got to put 5 here we are balancing it now, and now we got the proper amount of gain and lost electrons 5 each and what we have established is, the initial point of the balancing, we don't actually have it fully balanced yet. Now we go from here and just got one element till the time of oxidation numbers gives just the diving board and we just get jump of into the pool now, so one Mn one Mn 4 O's , O 4 O's 8 H's, 8 H's 5Fe's and 5Fe's and you'll say of we could done that before but you know what it was the Fe's and messed everything up, but heres the thing, look at the total charge one negative and 8 positives, well one start that's 7 positives so far in this side, plus 10 positive so 17 positive charges on this side, your equations balance in terms of charging the other side too, look 5 times 3 is 15 plus 2 is 17, there the oxidation numbers can help you balance even most difficult equations.