Learn about Senior Chemistry, Equilibrium 4, in this comprehensive video by bannanaiscool.
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Male Speaker: Lets put some numbers into an expression, and then kind of mess with the equations see what happens, okay watch, lets take H2 plus F2 makes HF all gases when they all go into the expression, this of course becomes square divided by the concentration of these two, now lets pretend that an equilibrium you have 2.0 moles per liter I'm using big M for moles per liter, you got big M or Mol over L either one is fine. May be got you teach you those so if that happens just play along its okay, and lets see that we have 1.0 moles per liter and 1.0 moles per liter here, so I said you okay if that's all the concentrations have equilibrium then what is the K value, quite simply we would just apply in the concentration here 2.0 but look you got a square don't forget, divided by the concentration 1.0 and that's 1.0 there, and of course that equals 4.0. That is that there is 2 squared over, one divided by one right, yeah okay, so the K value is four you don't have to worry about unit because actually its kind of fun, here there wouldn't be a unit, that's moles per liter square divided by moles per liter divide by moles per liters so there wouldn't be a unit but even if there was a unit sign just don't really care its just to messy, so we just knew the unit out, good. That value you right there, is consistent for this equation always, at a given temperature and as long as we don't mess with that equation, because look what happens if you did this, I don't want to go that's in like there, I want to, I want to take care of this and make it a 4, and then I want to make this 2 and 2 two, two four, does that actually change what we have for K value. Oh yes it does, yeah because then guess what will happen, this will be a 4, this will be a 2, this be a 2, so what will end up doing here it will if these are the same concentrations at equilibrium it will be 2 to the fourth power divided by one square divide by 1 square, so what's the answer are going to be there. Well 2 to the fourth power is actually 16, and so the answer for the K value is now 16, look heres what we did, we double the balancing but that means we squared everything here, so all we ended up doing was taking the original K value of 4, and squaring it to get 16. What ever you do in the balancing actually has an effect on the powers, right. To which the concentrations you are taking, so quite simply here is the idea, if you double the balancing take the original K value into square, what if you half the balancing from the original, well then, then you actually have one half here one half here, and one here, what would that actually do, you take the number four and it has to square root it, then I would give you two, if you are double the balancing you square the K if you half the balancing you square root, the K, if you actually changed all these and make these 3 times as much, in the equation everything will go up cubed, that's why you will have to cube what ever your K value is, that's all just take what you have done here, and make it a power to which you adjust the K valve. Also what happens when you took this equation reversely, would you get same K value no, you would have the reciprocal, so if you took this reaction, and reversed it, then you have to invert that or reciprocally and so your answer would be the reciprocal at 16, which is just one over 16. Reversed equation reciprocal, If you do any thing to the equation by multiplying by a number, take that number and make it to the power to which they K changes.