Gibbs Free Energy and Equilibrium Constant Ch 19 V7

追加: 2026-05-16

[00:00:00]okay so finally this chapter middle kept their relationship between Delta G standard and equilibrium constant for a reaction so we've been over about to calculate Delta G for a reaction under non-standard states now if that reaction is at equilibrium then the Delta G will be zero and so therefore the concentrations in the reaction quotient will be equal in concentration so Q will be equal to K so this will be 0 and then Q will be K so then Delta G standard is equal to minus RT natural log R K so there are two uses for Delta G standard that we have been calculating one is to get it on your way to get Delta G so that way you can see under two specified conditions the reactions spontaneous or not and how much energy can get out of it if it's spontaneous as it happens or how much energy you must put into it to make it spontaneous if it's no so that was one of the uses of this the other uses is that it's related to a global constant for a reaction so let's put that equation to work and see what we can do with it so again going back to the familiar reaction decomposition of let's still one by one the decomposition of calcium carbonate to calcium oxide and carbon dioxide so we were given the Delta G standard for this sometimes they don't even give you a delta G standard you have to figure out that all today each standard Delta s standard by looking at the values of the tables from that figure out the Delta G standard once you do that then you plug it in here and you solve and by then you're going to be tired you forgot that this is in kilojoules so make sure you convert it to to excessive important because our easy tricks that's what I might want to stay back this way so once you do that in yourself for natural log of K and that's e to the power of minus 52.4 which comes out to and that makes sense because the delta g standard for this reaction is very positive so the more positive Delta G standard for the reaction is the smaller and a value of K for that reaction which means that equilibrium you have very little products and mostly reactants so those types of reactions in chem 1a B is simply don't take place because you produce so little product that is almost negligible so if the delta g standard for a reaction is very positive that means that the hakuna constant for that reaction is very very very small which means that equilibrium you have very little products mostly reactants so you can whatever thought those reactions don't take place so that's one example let's look at and of course the reverse is also true so for a reaction that the nota G standard is very negative the value of K will become very large which means that equilibrium you have mostly products very little reactants so the concentration of your limiting reactant will be almost zero so for example those complex ion formation the formation constants for those was very large so for those reactions if you were to calculate the Delta G standard using the K formation you'll see the Delta G standard comes out to be very negative which means at equilibrium you have mostly products very little reactants so in chem one area so those reactions go all the way to completion so in here the second example you have a reaction I'm sorry you have a weak monoprotic acid its concentration is two molar and its pH is four and you want to calculate the Delta G standard for that reaction and so you set up the icebox like before and you calculate the kin so this is basically lady pretty much real to exam one so in exam one you learn to calculate the KA if the molarity and the pH were given so from the pH you can calculate the chlorine concentration of hydrogen is 10 to the power of minus 4 so that's the whole concentration hydrogen all you have the initial concentration of the acid and the hydrogen and the abaya and so then you set up the icebox and calculate decay which comes up to be 5 times 10 to power minus 9 so ka is very small what does that tell you about the Delta G standard for this well it must be very positive so we plug it into here and you solve for it and it comes out to plus forty seven thousand three hundred fifty six joules with only 3 sig figs when you come right into kilojoules is forty seven kilojoules per mole so it's possible so that's what you will get for this so the delta g standard for all weak acid organizations will be a very positive number like you see there same with KSP so those insoluble salts if you were to calculate the Delta G standard for those reactions like here the silver chloride says the solubility silver chloride in water at 25 degrees Celsius is 1.9 types of the department is 3 grams per liter calculate the delta g standard for this this delta g standard also must come out to be very positive like here why because the case the values are usually very small just by ka values just like 8 feet out so in order to do this again this also relates exempt to be much be able to exam to you have to go from solubility to molar solubility to KSP this is something that you did for exam two and then into Delta G standard so I'm gonna let you guys work on this it's very similar to what we did there so I'm gonna let you guys work of this and see what you come up with