Transcript for:
Weak Acid and Base Equilibria

now this part we get into the qualitative find the pH solve the problems using the weak acid equilibrium and use a KA equilibrium use a KA equilibria and the KA is acid equal them this is simplified form of the KA equilibrium because we instead of a writing down the hydronium we write down only the proton and all the bracket is for molarity and even with no subscript no subscript means zero or EQ it still means the equilibrium concentration it just because in this chapter we're deal with equilibrium no longer kinetics what he was increment and there are some basic assumptions when you solve the pH in the aqueous solutions water it actually because all ionization in a produced hydronium ion reformed hydronium ion but in our calculations neither hydronium or a hydroxide the initial concentration are significant enough they are not singing in that compared with how the outcome of the acid or base ionization these are these values in the 10 to the negative 7 more is very small compared with how the actual acid or base produce the ions they are negative or three to zero and the evil weak acid have a ka is very small then we considered the association's negligible that means the equivalent concentration equilibrium concentration of our acid it is essentially approximately the initial concentration very low percentage become ions the first assumption is actually more important the second there's some big like a small or large how small need to be there it's actually the need be quantified so we're gonna use the first assumption most and so the ionization of the week at that we can calculate the inclement concentrations sounds like we solve the quadratic equation in the last chapter and very similar the question asked about this weak acid give you ka what is the hydronium concentration which is same as a proton concentration open time it's very down proton concentration so to calculate this and we were given the K as you remember in the equilibrium Choppers you were EP you were given in K and try to find equivalent concentration open times solve a quadratic equation so here we go we sort of ice table first so when you solve the pH or dissociation problems equivalent problems in this choker and next chapter you are required to show the ice table so what that means you need to set up an equation first balanced and then the you show the change and the end all right down and this we have the KA given so we write down the KA equilibrium the K equilibrium it is the the acid which is HPR is in a short form for the proper in lauric acid the problem oil gas being the organic compound is named come from the propane and acid so it's basically propane acid which even though don't call propane acid and just HP are the reactions between the HP r and water the water often times we don't need to show that but - them all just show the water so here the acid applica acid keep the proton for water and since water take the protons water here act like a base the acid lose proton becomes a mile you get this and so that's equation all the equations balance because all the coefficients one and then we solve this equilibrium concentration by setup I stable so the initial concentration and you have the point 1 0 molar HP are so you need to concentrate at 8.10 the water is a liquid state so we don't consider concentration yeah as a matter of fact we don't consider water in the ice table calculations because water is not part of the including equal constant and at the beginning before dissociates hydronium concentration it should be ten to the negative seven because pure water it has ten 297 m hydronium but again use approximation from last slide with tree to zero that would treat this to zero before ionized there's no ions and ions come from there proximally acid since this one is also zero and then the change the change okay with since we did it in the last chapter it's easy to we don't know how much changes so that we add a negative thanks coalition's and want to make it 1x with the water works to show that even though we don't do any calculation let's just write this down and everyone the coefficient 1 so the X is just 1x cross reactant native ex and product politics and so we're just spinning up he's setting the endow the initial price change about point one zero minus X the water actually don't consider it's very large molar constant let's just cross this out we don't use a water for the end calculations and the hydronium x this I on PR negative ions also X in the air and then we set up an equation this equation it is using ka K equilibrium is for this equilibrium and you have the equivalent concentration of these two is x times X so x squared product over reactant if the liquid or solid state we treat them as one the DOE so the don't show in the equilibrium constant calculations and the reactant HP are the water a water's liquids that don't show the water just show the HP our HP are the end concentration point 1 0 minus X and the KA is given is a one point three 10 to the negative five okay so there we go we can actually just move on solve the quadratic equation well I don't think anyone's interest very motivated to solve quadratic equation for this because the number is actually fairly small it very difficult to work with we have a very small numbers so we can actually use the approximation so only if ok if X is very small if X smaller than the point 1 0 2 much smaller this can be approximate as the as 0.1 0 if X is very small how small well so far we don't have any idea any idea how the X will be because we have not solved equations we don't know how small X so lady based it right now we can just assume the X small X is very small and later we use the use X compared with the point 1 0 if this X is less than less than 5% over the point 1 0 then the X compared to the point 1 0 becomes negligible so later we need to verify we've had so far as soon X more but the criterion is the criterion is the X compared with the initial concentration of the acid this some 5% then we can use approximation okay so we keep this in mind first first we just protect X small solve it and then we go back to user criteria to evaluate our approximation okay so at this point we assume the X is small then that equation becomes x squared divided by the point 1 0 equals the K and then we solve X and that become very easy solve the X just simply equal square root of the KA which is one point three ten two million five times twenty one keep in mind so far this X is a approximation and we're not through the X is really good enough by solving this one it's a big major shortcut but anyway let's just go ahead solve this and then we evaluate see how our approximations okay go back to the criteria anyway we use approximation and it would pretend X is small we saw the eggs and so that X should equal the one point one point one or one point two it should be very small let's keep it proper so 1.3 my calculator need-a sudda need some light actually I'll turn on the lights did we do that 1.3 square root one point one four so one point and one around to one point one two sig figs one point one 10 to negative three and this is the X it has units because X is concentration suppose they're all right so we assumed X small and we solve a tentative this X is a tentative answer is this sounds a really close enough we use the solved approximated X plug in here so this is do the evaluation evaluation we use the approximation X which is a 1.1 10 to the negative 3 divided by divided by this this by the way is the word this is actually equals point one that's why in the general form is that putting here in this question the initial concentration of the acid HPR it is point 1 0 so let's we solve the X compared with the concentration the acid concentration and this will shows me is one point one percent and since you can see the does X compare with the concentration which is 0.1 less than five percent that means approximation is about it approximation is valid which basically means they solve X is accurate enough X is our financier and X it is the hydronium concentration so when we solve for the concentration of the hydronium ions on the weak acid with a given K we set up I stable and he was assumption the initial hydronium concentration equals zero because supposedly the dissociated hydronium ion it should be much higher than the neutral water which is tend to make him seven and that's why in the beginning we pretend zero it's basically means it's mine off and this of course here none of the acid become ion yes since there's no ions in the beginning and then we just solve it and you can see this is a very classic scenario we could have saved a solved by using the solvent quadrant equation but because the X the KA is so small ka is so small there is a very good chance will he use approximation just as long as they meet the criteria so this criterion words come from okay it come from here when the when the point 1 0 minus X under what circumstances can these two equal can point 1 0 minus X being approximated as point 1 0 it is when the X is much much smaller than point 1 0 then basically it be treated as a round off as X as if the X not a important yeah only when the ex compares the point one is small enough so you would ask what is container how would you say it's small enough it is a five-person ago when this compare was this a big chunk it's less than 5% of that then we use approximation and then use approximation then solving it's very easy so when you show the work for solving the concentrations eventually lead to pH the set of eyes table and use approximation but keep in mind you need to justify we need to justify our approximation so what is the criterion is when the change X which means how much how much of the acid dissociate compared with the initial concentration is more not then you have the basically the Associated acid is negligible and so the evaluation is basically as a trial and error you solve X by use approximation and then you compare the X with the initial concentration of the acid see we get a less than 5% even less than 5% then is it legit your results or the accurate enough some of you have time you might be able to you might want to try to solve quadratic equation and you notice after rounding out of sig figs applying the same thing around to promising things you will get basis same number compared with a use approximation so because that's the that's where the 5% rule come from when the five person rule is it's not a violated then they approximation keep it good enough results so solve the week after that we have use of approximation what is it general we have that okay so before I wrap up the we have equation is solved it's a more general formula for solving pH so with last ice table with last for ice table you solve with this ionization which is ka and usual concentration this is the concentration you get a negative eggs X plus X plus X and so forth and finally we what is the criterion the criterion is the X no bracket criterion is when the X compare with the acid concentration the initial concentration is less than 5% then you can use if the approximation you solve you have equation to do that which is K a x initial concentration of the acid H a subscript 0 means initial concentration of the acid this is basically approximation we argue is weak acid you use this equation as shortcut to find the H+ and then you can find creation so keep in mind it is you have a condition and conditions this it has to be smaller than 5% of the acid concentration otherwise otherwise solve a quadratic equation and you got two solutions and you throw away one of them and keep the other so it's a lot more work you might need to do that if the the X compares with initial acid concentration it's more than that person whatever that you need to do the quadratic equation some of the acid when the acid is very strong or when the solution is very very diluted this no longer holds the percent dissociate will be more than 5% then you need a new the quadratic equation to solve in our class we rarely ask you to do this but we in the EP in the quiz or test and in the situation that you need to use some quadratic equations keep in mind that the same way as we deal with the last chapter the chemical equilibrium and you solve quadratic equations for some of the simpler equivalence okay next one fine kad weak-ass from sodium th-this is a basically reverse of the last question the last question give you K and a finer H+ and this question give you the pH and they find K so now we have pH is 2.6 to find a KA of the acid this will still write down the equilibrium the KA equilibrium a different acid with water will give you hydronium as a acid it lose a spot and water gains each hospital hydronium and the acid becomes an ion so with this we have this we can still use I stable but in many cases people use their approximation but anyway here we showed you you need some more already of the acid is 0.12 so there's 1 point 1 2 water we don't consider I don't consider water in the whole scenario because it changes very negligible a hydronium in the beginning zero zero and X and X that's the same as we saw before yes so in the end of X X and the the acid becomes point 1 2 minus X so that's how the equilibrium looks like and so for this equilibrium the KA is should be the product which is hydronium and Ana so X square divided by the acid my index the point 1 2 minus X means at the equilibrium how much are the molecules the concentration remains we'll lose some of the acid because those part of acid become ions becomes hydronium and dni what is the X as X is hydronium concentration so if we solve the X then the K can be easy to solve and now we have ph h plus N equals 10 negative pH 10 raised to the negative power and so use our calculator make it to 0.62 and so the X X it'll be equals 10 to the negative 3 and this part number I cannot remember that so let's do that what I get is 2 point ok the exponent have 2 decimals okay exponent have 2 decimals so the answer in the scientific notation this one part should have the same as how many decimal places somebody's if the number of sig figs should be two sig figs 2.4 and that is how I solve the X you the pH and once you solve the X may be easy to solve decay X is the 2.4 10 to make a 3 square and use a point of 1 2 minus and final answer the keep only 2 sig figs because here's a 2 sig figs and this party halves abstraction and this is very small you know another 2 sig figs so to say we divided it was like final two sick days in decay so I have a square of that divided by 0.1 to 176 so what I get keep a two sig fig is 4.9 10 to negative 5 so that's the KA from the secret any questions you guys all get a number that wouldn't seem much easier because technically we were already given X yeah yeah yeah if you use e there's an even shorter sort of cut than this he remember use approximation and since we have the X you use exterior lighting calculation which is the point 1 2 you care about a how about % it looks like only 2 percent but it's only about 2 percent that means that we can use approximation use approximation that is we have just that we around that equation okay you don't need to do this but just kind of showed you that we have with this approximation it would be give me good results even percent less than 5% which is stro so that means this equation rearranged you'll get a ka post h cross divided by the acid concentration which is exactly the same as we did here but you can see this is use approximation if you do that you get a basis same results you see the same results I got four point eight and so that means the law get a little bit off that's because you use approximation so that's why in this chapter the would make great questions I ask you only submit your answer adam-11 decimals for pH because one decimal two dozen one place becomes a new number chain can be very noticeable like just for my name for mine use approximating kids this the precise number should be this but it's kind of interesting even though it's point 1 2 minus 2 point 4 10 2 minutes we definitely around it it's pretty much as that point 1 2 so like on the quiz which answer should we put the 4.8 4.9 in the quiz that's why the most cases a skew only submit one decimal place for pH and one sig fig for the K for K once it bakes it's close enough I see so the answer just would have been fine basically it's supposed to keep to saying things per rule but it because the rounding it'll give you a slight difference it's very small for this question that 4.54 in mind the difference is about two percent by the between this and this numbers difference is two percent can I see there's them all the toolbars are popping up nice okay yeah between 4.8 4.9 the difference is 2% yeah which has come from the this tiny piece come from this piece if you are shoe shoulder full work yes you gotta follow rules and keep every step to promise a face you can just fit in one blank then there's degrees of it's not a major problem in in our quiz because all the quiz I have manually graded your work percent dissociation okay percent dissociation it is basic how much dissociated divided by the total amount of full amount in each wall mount and [Music] if the concentration decreases the percent D social actually increase the reason is because percent dissociated it is 2x in our ice table this part it is same as X its X it come from the dissociation of the acid salt X or proton concentration divided by initial concentration it is percent dissociation and how come there's a acid concentration decrease percentage increase is because if you use X the X is ka times initial concentration of acid and that divided by initial concentration of acid we got this and then we'll combine together becomes that so you can see the percent dissociation which come from this piece it is inversely proportional to the square root of the acid so that's why the acid concentration constant decreased the final percent actually increases and also we can use the sophia's principle to explain that we have a disequilibrium and the increased concentration so when you want the constant decrease then the you have less of Bose product Bose program decrease it'll actually favor that you Clement ship to right will decrease these two concentration the good explanation for this it should come from the delusion in fact the diluting in fact is one of the sharpest principles prediction so anyway we need to know how to calculate percent dissociation and as for how does percent diesel dissociating change with concentration that come from the come from this equation personal decision it should be the H X and we just learn about X which is the proton in equals that the square root of things and that divided by the whole giving person D so chain rearranged I give you this and that you can see as a concentration decrease the percent dissociation increases so that's the person dissociation the percent dissociation is depending on the K we have a large K you have higher degrees of dissociation as you can see from this equation equation increase k % associated increases and so the other effect decreases the concentration make a note diluted that also helped dissociate so that's the person dissociation and how that how does that depends on the concentration okay well she's she's some how do we calculate percent dissociation and then move on so we have a same acid pH as such what is the percentage association this is a continuation you the same numerical values from the last or the last example so we can just borrow those example the is a weak acid and instead of asking for the KA we asked what is the person dissociate itself in percent so the associate percent it should be the dissociated / the full amount of acid the origin amount zero the initial times hundreds and the percent dissociated it is the X in the nice table percent dissociated for the weak acid it is the concentration proton in the ice table in the rise table these two will equal the or equals to X at equilibrium so that's why the dissociate which is this part in a single X and we have a equation star use the approximation that's if we have to solve the case and solve the H possibly you'd like this but in this question we don't need to because the pH is given P is given that you can simply just use pH find the H+ okay this numbers come from pH which we solved in the last last slide so we go back h plus we solved X which is two point four 10 - - thank you sir that's the way you solve a math example so go back here we use the 10 raise to power of mega pH two point four ten Thank You Street and divided by the initial acid which is the point 1 2 so by solving this we get 12 1 0 percent so that's the final answer for the percent dissociation it's two point zero so the percent dissociation with the weak-ass how you know the amount of acid dissociated it is equals the amount of ions and ions come from the dissociation which is same as the H cross because study geometry one mole to h plus it produces one mole of the proton and and one mole of the anion PACA - so we nanak install a set of the use the hiline concentration to substitute the dissociation Associated acid and find the percent dissociation any questions on this percentage association from the from the ph we can also calculate the percent dissociation use use this that will give me the general kilometer for the weak acid association the general format we use in the the acid concentration which is K times use the approximation the environment by the H a the initial concentration and times 107 and that if you simplify by giving the very nice that's the general formula finally sort of person the Association so as you can see again from here the example percent dissociation it is an equivalent constant over the concentration square root so as you learn okay logic aid then you have a higher percent dissociation or lower concentration of the acid the lower concentration solution more diluted it helped dissociate so that's where the weak acid polyprotic acid on the acid can release more than one protons and there's quite a few Polidori acid and they are very popular so for example carbonic acid is the diaper t acid have a three protons two protons and the phosphoric acid is has a three protons tribe triprotic acid and they can all release more than one and they're read associations is actually have more than one steps the very first step phosphoric acid with water give you dihydrogen phosphate so the as and become counted base water become counted as a hydronium ion and this equivalent constant we call ka one because that's the first step association okay and this number is very large ten and eighty-three next step the dihydrogen phosphate can dissociate releasing more protons and that becomes the conjugate base which is hydrogen phosphate the second step equilibrium constant is a KA to and you can see the Kate who's much more k-o-k you won and it can move on continue the hydrogen phosphate giveaway last proton become phosphate ion and the case 3 is even smaller so there's a reason why the progressive dissociation and every the second step and the third step but most smaller K is because the attraction between the between ions the attraction between the hydrogen protein and the protein rhodium they do the charge the tool that's a one-pass charge so the attraction between these two it's much stronger stronger than the first pair first pair is a one to one to one charge single on to charge minus -2 charge attract a one positive charge stronger attraction so made heart disease to dissociate and when you get to the phosphate phosphate ions 3 minus charge and this 3 minus attract them one positive the attraction is stronger than the to natal chart attract one you see their KA is even smaller it's harder to dissociate separate these two ions because the electrostatic attraction it becomes stronger so it's just because the charge main factor is a charge attraction later dissociation you're having a higher charge attraction so more difficult with dissociate the pond protein acid there are some calculations you can see from the book and I will not go into the too much detail about a poly-cotton acid calculated final pH basically calculation as a two steps you have first step dissociated and you consider second step it's very good example how to use ice table to solve real world problems and these are some particle P acid and you can see the k1 typically the largest and pay to smaller if there's k3 the pastry's even more even smaller one of the very good polyprotic acid it's not me here the citric acid because citric acid is solid and it does come from plant yeah well manufacturer citric acid what can you use the citric acid from the lemon juice or orange juice they have citric acid it has three protons to dissociate okay weak base the weak base typically the wheat-based are the compound or markers have lump hair and they can form bond with Croton and that the base with long hair it can form bond with H+ ion and this reaction the the base molecule receive protons water act like an acid okay water here are like acid in lose H+ to the B and so water become hydroxide and the B become BH plus sometimes we write down HB plus is the same thing because he's a generic formula for the county acid from base and this equilibrium we call KB equilibrium because it produces hydroxide where's the hydroxide will will eliminate the the proton makes the solution basic this solution make the water more basic because in a formal hydroxide that's why I called KB program and KB equilibrium the expression just like the KA we don't consider water you have the hydroxide times the County the acid HP plus or pH cross over the initial base concentration so this is KB what looks like and you can do the same way you find a PK B is negative R 10 of the KB you can PK and so the higher KB means a stronger base and higher PK b it means lower smaller TV which means a weaker base high PK b means weaker base it's just like a PK n K so in this reaction the base make the water turn to basic it's not because dissociation mainly because the base take the proton from water it turned the water into hydroxide that's why it makes the water basic it's not dissociation it is actually the water is stripped of one proton become hydroxide with a weak base we can do similar calculations similar equations ice table approximation to solve the hydroxide ions and then eventually find pH just very similar and but before doing that let's see what's happening in those reactions here is another weak base the methylamine is organic molecule and the nitrogen here have one bond with carbon the other two bond with hydrogen it has a one lone pair on the nitrogen so here's a pair might have a overlong here and when this one take the protons from water it take away the proton from water the I mean nitrogen now I have three hydrogens three hydrogens because gained one proton from water and the water lost this one proton and becomes hydroxide this reactant very similar to the ammonia reaction with water it gives hydroxide that's what about KB's you can see there's a whole bunch of KB's not needing them they memorize ok we do not need to memorize any of those paddles but just kind of appreciate yeah the relative strength that regular strength the first one you can see they have a relative higher kb than all the rest ammonia is a very popular base 10 then megapix it's very weak base and there's more base of the organic compound you can see all these compound are organic except ammonia because ammonia does not have a carbon in the market and so these are some weaker bases the caffeine is one of the weak base caffeine it has the module nitrogen's and those nitrogen have lone pairs and those lone pair can take proton from from water produce hydroxide ions so solve th for the weak base the we just went over the saw th for the weak acid okay we work use I stable and then use approximation and once you use approximation we solve and the evaluate we use a 5% rule same thing applies to here as you can see the equilibrium looks very similar the quadratic equation even that looks very similar so we use the same rule to evaluate if our approximations about it okay so we have a time methylamine its organic market and this KB is five point nine ten ninety four very strong base what is the pH 1.5 am toothpaste water pump on violent as upon pH basically we need to find any H past this equipped equilibrium we have that we see the KB by the KB did not give us proton or hydronium KB is equivalent that it produced hydroxide so the plan should be we want to find a pH so that means I need an express H cross is not given in the equilibrium but the hydroxide if we can solve from hydroxide I can use kW to solve for H past so here's a game plan the plan is we need to write down the the KB equilibrium for the weak base and instead of ice table instead of a change to X and solve the X hopefully not using quadratic equation it use approximation and then once you verify once justify the approximation then the hydroxide ion I can use kW to find the H+ and then finally he was pH so for the weak base that's the plot how how I should do this and let's write down the equation for the sweet base the dimethylamine it's big name so let's just D hey that I messy I mean all right this one with water see this question give you Kb so you should write down the equilibrium that has a hydroxide one of the product will be the hydroxide this hydroxide come from water and then the DNA is the weak base once combined the H+ this will be the counter acid for this DMA so that's the equilibrium for for this reaction it produces hydroxide because K be the equilibrium constant for this reaction it is KB okay and this is KB we have water liquid so later we'll don't show them in the calculations or the equilibrium expression let's just say the ice table you can see the eyes table is very similar when you solve the quiz or a test question find pH you basically do the same you write down the reaction and the ice the initial concentration is a 1.5 we'll just use this number water we do not use for any calculations later let's cross this out hydroxide suppose we tend to menu 7 again we use approximation we pretend this is zero the hydroxide concentration after you solve that in almost all the cases you notice hydroxide concentration in the end is much higher than 10 to native 7 so that's why it's the legit to keep in the freedom 0 to small negligible and saimin of course no ions in the beginning target zero and the change then you X plus X plus X that looks exactly the same as the acid ionization and it is even the equations of solved hydroxide looks similar and then you know plus change this one you know zero so don't believe yourself all right with this looking to set of equation a KB should equal the end concentration of these two they multiply so become X square divided by 1.5 minus X the equivalent concentration of the base and this concentration we get is the equilibrium constant is five point nine ten to the negative four so let's use approximation later but don't forget use the 5% rule to evaluate to justify the approximation if the X compared 1.5 it's in less than five percent then this should give us good results good enough so this is the equation I use approximation that becomes X square simple just a bump point five and we pretend so probably attended X's them small enough compared with 1.5 then just become bad okay so here's a solving to become very easy looks familiar because the x squared or the X is certainly just square root from one point five times the KB and you should get that almost a sweet yeah so use a decimal that would be keep only two sig figs keep on to safety you keep two that'll give me three point zero 10 to the negative 2 times X you can add a unit or you can add a unit later so that we solve this first let's do the evaluation so just X if compared with 1.5 let's send the 5 percent of the 1.5 that this approximation is valid so let's do that let's use X divided by 1.5 the x divided by the initial concentration okay remember the X is dissociated base spacer so the dissociated compare the total 3.0 times 10 to make it to the invited by the 1.5 and that'll give me Oh again exactly two percent two percent so that means approximations is about it and then we can get the final answer the X is three point zero to ninety two the hydroxide is X and then since we pass the five percent test the X true value it is the one use approximation hydroxide is 3.0 tend to make two and because the past test the approximations is good enough he associated base it less than five hours in less than 5% of the total base so this approximation use this equation takes screws give us good enough results you the approximation is seems like something new because in the intro camp and 180 what buying any cost we almost never use approximation because you're not review is a complicated not at advanced math but once you have the you just use a quadratic equation to solve problems that becomes an issue it's becoming inconvenient and now realize is actually not necessary by using approximation it'll give us good enough results and especially the when you consider how many sig figs save eggs means your round you round the results after rounding the approximation compared with true value has essentially no difference and since there's a shorter there's some easy way to handle that there no need of using the quadratic equation for most questions and so with the hydroxide that we saw and once we solve hydroxide question asks about pH okay there's a major shortcut we don't need to find the H crust and then find that pH we can simply just find the Poh from here and then use a 14 - Poh to find pH so here is a major shortcut you can do both ways okay you don't have it go this way doing Poh is actually easier toh use the solved X which is 3.0 10 - maybe to find a Poh and then pH 14.00 - toh all right so let's find the Poh first and so that Poh negative log of the three point here 10 to 90 to keep two decimal places okay keep 2005 and what I get is a positive one point five to two sig figs I have to take the logarithm become a to two decimal place that's what a Poh will be and then use the 14.00 - eh to get pH so this is actually a easier way to find a P find that the pH from hydroxide molarity the other way the other way is found across first kW the water auto-ionization constant is a one point zero zero 10 to negative 14 divided by hydroxide which is you just over here and then you find a pH so either way both ways should have work the same and actually the 10 to the negative 14 this chunk it is where the 14.00 come from so remember that this is the earlier part in today's in the class what mentions all the h plus Poh and pH this morning we actually cover a lot of stuff and we have quite a few constant K KB and kW solve quadratic equations or use approximation for the most farmers will use approximation but just remember to do the validation the 5% rule so here basically how do you know the approximation it is when the X divided by initial concentration base with the one point five if that's less than 5% the approximations the trip the part may be good so that space of the morning our main topics we have a the weak acid and a weak base and both case use the ice table and use approximation approximation and validation to avoid kind of to avoid the quadratic equation okay either case if the x divided by the initial concentration of the either acid or base more than 5% then use a quadratic equation solver variant question and so basic that is the this morning our topics up to here