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Lecture 11. Buffered Solutions (Buffers) Pt. 2.


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Title Lecture 11. Buffered Solutions (Buffers) Pt. 2.
Title of Series Chemistry 1C: General Chemistry
Part Number 11
Number of Parts 26
Author Arasasingham, Ramesh D.
License CC Attribution - ShareAlike 3.0 USA:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor and the work or content is shared also in adapted form only under the conditions of this license.
DOI 10.5446/19000
Publisher University of California Irvine (UCI)
Release Date 2013
Language English

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Subject Area Chemistry
Abstract UCI Chem 1C General Chemistry (Spring 2013) Lec 11. General Chemistry -- Buffered Solutions -- Part 2 Instructor: Ramesh D. Arasasingham, Ph.D. Description: UCI Chem 1C is the third and final quarter of General Chemistry series and covers the following topics: equilibria, aqueous acid-base equilibria, solubility equilibria, oxidation reduction reactions, electrochemistry; kinetics; special topics. Index of Topics: 0:00:00 Titrations Review 0:10:14 Types of Titration 0:11:47 Strong Acid added to Strong Base Titration 0:32:35 Strong Base added to Strong Acid Titration 0:46:21 Finding Volume of Excess OH-
OK can I had everyone's attention please so let's go ahead and start I wanted to remind you that your midterm scorers already posted on the class website on as we speak your exams of being scanned and within a few days you will receive a PDF file of your great exams are right so if you have any questions about the grading should wait until we received a PDF file at and exam and then take a look at it but in the meantime it is important that we got a discussion this week because during discussions this week we will actually go to the answers From the exam and I would remind you guys that this is important because this is the 1st major and I want to make sure they get feedback on your performance on the exams of the tears point out to you mistakes that students may we have greater fairly strict .period so most of the questions were the wider wrong so you have to get the entire question correctly all right I must confess that the classes really well I am really pleased right that the scores were good exam was not an easy task to sell world-class did very well and I think could use for you guys but I remember the battle is not over and this is just the 1st time and we need to get through the whole quarter so I want you to keep that momentum are right and so please go discussion this week that he is will go to the answer came with you if you have any questions they answer those questions they're the ones who graded examined I'll tell you how the exam was graded as well and this is important because I want to have that information as you prepare for the 2nd midterms because that's how you exams will be graded on a 2nd term as well OK now before I proceed does anybody have any questions great itself you don't know what is going to pick up where we stopped and last time we talked about acid-base titration and the timing is pretty good because I understand you're doing that in lab right now OK so if you take asked titration in general titration we said on analytical tools it's a tool used to analyze or determine the concentration of an unknown substance or element in a solution arrived so we wanted to determine the concentration of the amount of a substance in the solution we have to take advantage of a reaction arrived and titration take advantage of a reaction that has to be very clean no side reactions are still reaction taking place so it has to be a reaction that clean it has to be quantitatively which means that has to be react completely and thoroughly has to be rapid you can't sit there for days waiting for the reaction good completion so we take advantage of reactions that are clean quantitative and rapid and so it turns out acid-base these reactions are ideal for this because Aceves reactions to react rapidly cleanly and quantitatively OK so we need looking at titration we look at reaction where 1 of the reactants you know what the concentration is all right and the solution with the known concentration the reacted with the known concentration is always placed in the beer and that is called the title we place the solution of the unknown concentrations in their life last and we call that the and and then what you do it is you carefully measure amounts of the type trend into the analyzed so carefully that will be used in the Europe to carefully measure volumes the tight turns into the analyze and you make somebody well so that the reaction was to completion
right at some point as you add tightened incrementally there's going to come a point where the reaction goes to completion and when the reaction was to completion it signaled by some change physical properties so it turns out can use many different physical properties to signal where the titration goes to completion now the most common way to do that is to add another reagent which recalling indicated and the laboratory you would have carried out an acid-base titration where you added the North Island as the indicator and so did your satellite is an asset when you add the Roma the do not indicated it's colorless and then you add the beets incubated the base there comes a point at which the acid in the base would have reacted completely so that now at some point you have a slight excessive base to the ending of the biggest in increments didn't come to the point where I didn't have a slight excessively or with the acid are right at that point you indicated turns pink alright because they not the Ireland is colorless when the solutions the city but it turns pink when the solution is basing so when all the acid has been used up the reactions and now all you have is just a little bit of excess base in there then the solution things and that indicates that's the reaction is completed a so that indicated another way there were another physical property that you can use to signal the completion of the reaction is to look at the pH remember you haven't asked looking at Aceves titration than if place the acid as in the last and appeared to me Inupiat meters you guys have used the to meters that it has electrodes with electrodes in the solution and then the meter reads out what appeared to that solution and if you have an acid in their watching the pH read less than 7 7 agreements have lessons so To begin with the only acid there and you're going to read a really low pH nor as you have the baby what's going to happen is that the will react to the acid which and so the Assamese concealed so the kids will go up all right and so what look at is the role the change in pH so incrementally you add the base to the acid and appeared to me that you read the pH and then you can plot out we call a titration screwed alright and he said titration curve is a lot so you look at the titration curves a titration occurred it is of a lot of the pH of the analyze it's alright so this is what is in the flask as a function of the volumes of tight trend which is in the bureau added rights if you make a plot that th as a function of the volume of tight added usually witnesses in leaders all right if you make a plot of this we call this lot a titration curves are so instead of what he did in the laboratory you I think giving both in the laboratory where you can look at the not using an indicator that 1 way of carrying out tactician where the physical property that you're looking at is adding a 3rd region which recalling indicator or the other way it is to measure the pH meter in there and measure the change in pH as you add the title is that could written so it turns out that acid-base titration is committee of 3 types I going to look at asset-based like traditions in detail and the reason we're looking at acid-base titration is because I would have liked everything that we've learned at this point I I remember we looked at the the fact that you now know how to capture the pH a week after undercover defeated a strong as you know how it happened the future weak based you know how to capture the pH was strong base you know how to can be the key to the buffet I right so this is 1 place wouldn't apply everything that we learned what mix them together with a look at how to these changes as you progress of all right and so this is a very useful application of all the concepts that we take so it turns out that Aceves titration certainly of 3 types and the 1st is a strong acid where is as strong is the 2nd year is weak acid strong the 3rd is weakened base strong said turns out they can be of 3 types depending on what is a type trend and what is the analyze it you can have both been strong second-half titration with strong acid strongly a right 1 of them will be the analyze the other would be the territory Kent Oregon have weak acid were so strong base in this case the weak acid is the analyze and a strong base is the title for or the reverse way the week places the analyze and the strong acid is the type of case no we never look at titration is between weak acids we bases because you can't get any meaningful information out of it so you can't do titration with we gasses both being we are right so that they have to both the strong 1 is weak and the other dropped again so meticulous look at each 1 of these will start looking at the 1st of these wages a strong acid versus strong base and instead of using the idea fear not Ireland has the indicator would not look at pH titration curves right so we want look at tactician curves and 1 look at the dependence of pH because that's what we think happened along as the bottom of Titan has been added 10 so you can see that if I wanted a strong embarrassed classic strong acids strong base would be ACL 8 quest Mercer on any awaits all right and let's say
to begin with we will start with an example where a tight trend is going to be the base OK so we're going to start with .period 1 molar any OH cell member that is the the known concentration of in the flask women of the ACM it was so what we have here is a strong basis the tide turned and strong acid as the analyze a so as all of you know we have a strong acid and strong base and the combined them and all of you recognize a member of the large amount strong acids producers had to remain strong bases like outside produces hydroxide and we know that large amounts of Georgia mind and hydroxide and chemicals that's what they do you need less each other what they form a lot of pain they can coexist in small amounts like in what it's like tents the negative 7 so high during a mine and hydroxide can coexist only in very small amounts of right of the order tend to make it 7 otherwise we have large amounts of them they're going to react with each other and neutralize each other and for water so let's look at what the reaction would be followed you recognize that if we want to look at ways of looking at what we call the net finding equation so sold look at all the major species that we started at the beginning In a look at the major species after the titration has occurred the day after added the Indiana so we have a strong acid all of you know what we know about strong acids strong acids do work dissociate completely dehydrated lines and call so we know that 2 the initial the seal that we started with will give me 8 3 0 plus concentration and that should be initial seal
minds concentration as well and we know that the initial concentration of sodium hydroxide because a
strong base any dissociate completely she gave me initial concentration of
hydroxide and because we have the same amount of sodium and hydroxide they should all be the same OK so to begin with I have aged 3 or class it was Placido minus the quest this is what's in the glass it's a strong acid associated completely so this is the season of last nite by sodium hydroxide to that I have sodium hydroxide that has dissociated itself before any reaction starts the instant I combine them and have all 4 species in there is every recognize that are right but we now that because the strong acid we have lots of the and strong base we have lots of them and they cannot coexist so the instantly combined these 2 of the reactor cleanly rapidly and quantitatively To give me 1 H 2 0 and then I have sodium and chloride the Inacio is assault and once again the soluble salt and we'll solstice associate completely so what I would have it is if you want to look at this this is not the net and integration of sorry this is the complete mean equation 7 you look at the complete I'm equation this is what I have these other species to begin work at the end of the reaction this is what I would have now you look at the user concede that really so it was there at the beginning it's there at the end chloride is the the beginning "quotation mark right there the end secularism that sodium and chloride and not doing anything at all this time around are at the beginning of the that the end not undergoing any change at all and so we call them these are called spectator you can see that it is the beginning of the end and therefore there are signs that don't do anything at all so that spectators not participating In the actual events that are taking place and so we called inspected right now we might cancel out the suspected crimes because of speculation that the the the beginning there there at the end when I end up with is what I call the next question and so on what we have is over here the net finding equation in the net and equation we cancel perspective right because the expected rise to participate in the reaction are I survived take the net energy equation that describes was some arises exactly what's going on in this reaction and soaring acid-base reactions essentially what happens the acid in the face react with each other to give water right now you wonder the the general form of the equation the general foreman equation is sometimes very misleading so the general reaction would be we started with ABC our plus any awaits giving you 2 plus in a Seattle so often you would see the general form of the reaction raised you right on the 2 reactors and the products that are formed and you can see the generals from the reactor doesn't really convey what's going on because you know that it has a strong acid associates completely and they owe it has a strong base and associates completely different you water and we know that the salt that's produced which is an ACL in associated as well a case just gives you the general form but does not give you the details of what's going on but it's worth to remember that in past when you combine Pasadena-based you always end up with water and salt all right and that's what that reaction ,comma summarizes that we take this this acid in basic environment idiot water and insulting formed 10 so now what we're going to do is willing to apply what we learned so we all that the bottom line is that the reaction that really takes place is really the high during line the strong acids and the hydroxide from the strong base combined to give you water appeared so that's what we're looking at another go back I would look at an example in the example that will look at it as With established . 1 molar annual wage right and people were here women have been CIA but usually In a titration remember that and like concentration is unknown all right but because the practice and as a mental exercise what will to do is usually an experiment your you are an alive is unknown and which measures pH what they do is when calculated with the pH would be all right it will accompany the pH that solution then we need to know the concentration of the candlelight as well so what we have here he has 100 ml of . 1 molar each said usually the acid-base titration and you do not know what the concentration of the Allied is that what you're trying to figure out but he overdue is where trying to figure out what the pH that solutions but before we do that I want to show you the process and so let's really just look at what you have done in the laboratory all right so
yeah for all musician with Poland ml more than half of the people in the last 2 books you on other users change this year on the leaders of the thing there is a list of this so what solution of loans and in the but is to use until he used to have 1 thing in common that decision going on USA will hold its head and he will hold the 1st this year the people in the In addition to mediation urinal as this so you didn't that the solution be on the changes the is long so the end result is that I wanted to show you that grew so the in the laboratory carrier that experiment with you had was an unknown solution of the acid you had the pH of electoral placed inside the solution and you manage the peach and so what you did was you plot amid applause Of the pH that you measured as you added a five-minute milliliter increments of the base to the acid in a new plotted pH those on the volume of tightened added and the end result did you would end up with a titration curves and the titration curves looks
something like that so here is the titration curves for when you have an acid in the flask and you tightened dissipates became so let's look at this point here but that's the point here is that for you added any base so you would expect all you have in the flask is just as strong acid and therefore you would explain expected variable pitch are right and you can see that the pH is somewhere around 1 OK now as you incrementally add and titration is a strong acid Rice's a strong base in the shape of his career comes out to be this S shape could recall that a signal are right and you will see that initially of flask it is going to have assets of your pH is going to be very very well because the solution is possible but as you approach the end of the titration aware that the 2 reactors are reacting in Stoke electric amounted about similar amounts then what happened inside the pH changes dramatically and son using the rising pH Wright and then once you've passed equivalence .period now it's slopes are itself when the 2 reagents the strong acid and strong base have reacted completely with each other we call that the equivalence .period or the stoic geometry .period alright equivalents .period is when they have both reacted In an equivalent amounts recall that the cost .period sometimes in the laboratory you use the word endpoint right now it's important to know that the endpoint and equivalence .period actually convey different information the end .period refers to when you indicated for using an indicator the endpoint refers to when the indicator changes color all right and equivalent .period refers to when they have reacted in equivalent .period slot in some experiments the Cuomo's pointed end point will be the same In other words they will be different right now let's take brought on the final day example member of the not that changes color not when they have reacted completely with each other to note that changes color when you have a slight excessive debates because remember when you add the base do not have any colorless it's acidic it's colors of it's neutral but only changes college basic see them and so when you add female talent as the indicator the endpoint is actually when you have added a very slight success of the babies that's what we needed did the experiment remember you add sediment outside history to you added in increments and as you approach the end point you actually had have to drop get half drop it did you guys than that in the laboratory you can't let a drop hanging just halfway there then you take the liberty of lasting kind of get that have dropped in there and then used during a raid and so when you approach the end point you actually when add drops now you add half drops so that there comes a point in which we see the 1st traces of the slightest thing that means us in .period so there have dropped that you added it has to be subtracted because remember it turns pink only when you've added a slightly assessed so that's why you do it in half drops and have dropped as about . 0 5 ml all right so you led a pendant drop hang on the tip of the bureau just to have to drop in the take the philosophy into the flask and touch it and then you take it off until didn't you mix that half a drop of base that mattered and so at that point given see the 1st traces of pale pink if you gets from adopting new gone way past the point of no help their time you have to see the 1st race of a permanent pink because initially as dropped calls and the social 10 bank during illegal always all right and so on the 1st time and see the faintest of the faintest pink that's when the endpoint is and then if you really want to know what the .period was you take the end point use of trash the half a drop that you added weight to so I think and that would be the equivalence .period so that's why it's important that you realize that to end .period refers to when using an indicator and the point at which the indicator changes color very often where they indicate changes color is not the the same as the acquittals .period Boquillas .period Augustin geometry .period is when the 2 regions have reacted exact amounts all right so let's take a look at this that the equivalent .period here now we know that this is the reaction that's taking place we know that when you have a strong acid astronomy is reacting and equivalent .period all of this has reacted completely with that so I .period would once have been solutions can you tell me initially to begin with lots of assets story of base and equivalence .period now you added exactly the right amount for all the acid In all the babies to neutralize each other so that they could lose .period what would you have solution water and salt sodium and chloride water is neutral it losses 1 medal neutral seal minus is what the conjugate base of a strong acid content of its of strong acids what neutral basic as a neutral so what should the PhD at the close .period 7 so you know Nigeria tightened strong acid a strong base you know that the Collins .period has to be when the teachers 7 so all you have to do is plot this grass and have you got working at 7 AM and to to go with the volume is and that would be the volume of base that you can added when all the strong acid was completely neutralized with the strong base and that would be the equivalence .period alright chemistry .period self 1 important take a message is that you need to know what he calls .period is a strict geometry .period years and you need to know at any point in and make different again OK so now that we know what the plot should look like we're stuck calculating its all right and because now we're not doing an experiment anymore now woodland fairy world predetermine what the concentration of the acid is within a predetermined what the concentration the bases and it with account for of the pH usually we measure that niche all right and we don't know what the concentration of the analyzer that the experiment as but now in class was going to do with this we know the conservation began life as we know the concentration the title will be capital with appear to that solution should be dated so that we can win Sunday and have you help me out so we're looking at several scenarios women look at How I covered the appeared before I had any base I don't cover the period after it added somebody's hard like help with the pH when we had the equivalent .period and have worked out the pH when I have exceeded the caller's .period and I have a lot of Texas-based that could so let's start with the 1st which it is put it before addition the a bit so let's see if I wanted to point where relates Seattle and put a pH electrode in their 90 I measure the pH I should be able to calculate the pH that my pH meter should read or write so all we have in here it is a strong acid wonders the that solution 1
minute what is appeared to that still solution you know what is appeared that solution however is 1 study 1 wife it's . 1 bowler tend to like the 1 that the strong acid strong as associate completely and so by now I need you guys to know this otherwise I have to send you back to can 1 be right because we've done many problems you know that a strong acid and so on what I have to is is that we have initial concentration of ACL is . 1 more alert and we know that the walls initial concentration the high journeyman because we know strong acid associates completely an amendment that means that is 1 times 10 the negative 1 . 1 this 1 time Stanton therefore Kate tradition 1 goes to 3 decimal because our concentration is given 2 3 significant right so that began when we know the key to the solution in the flask right now an account with appear to the solution if I had said thirdly milliliters of any owing to the 2nd case is pH after 30 ml of . 1 more alert and awake member this is the tightened is it added OK so what we have to keep in mind that this is not if I wanted to figure out the pH of the analyze because of measuring appeared to be ECL after you added 30 ml of the CIA you want to keep in mind that in titration because we're adding base all the time to be analyzed see the bong exchange alright if the volume changes what is that tells about concentration what is the definition of concentration molds divided by volume you so if the mind keeps changing what is that tell you about the concentration it would keep changing all the time our and because of all is going to be keeps changing all the time but would keep in mind is that what doesn't change the walls of acid in the of based said soul and have to do is actually instead of looking at in terms of concentration up to this point every example of the problem that we dealt with look at we gasses encountered the pH when we looked at week basically covered the period when we looked at strong acids strong bases and even when we looked at BofA's 1 assumptions that we made was the ball never changed so the volume doesn't change we the concentration does not know we can keep the concentrations and we calculate them based on the concentrations because they're not changing altogether you understand here because we keep adding more and more base enough last the volume of class is continuously changing and continuously changing the concentration is continuously changing as well so we need to do is actually Catholic the mall rather than the concentration of the Silverado is willing to calculate the malls of acid so Member of the Wedding remember this is what I talked to last quarter memory concentration of polarity is always malls times volumes that's all you need to remember so I to calculate malls what is that the concentration times volume and memorable concentration always moles per liter .period is a unit of volume leaders I have to make sure always at the my bombings and leaders became so you might want to calculate their initial malls silent calculated that initial moles of Hydro near eyes and remember what is a universal symbol for mall it's a Lotus and alright survived captivating high during my concentration 8 steals a strong acids and associates completely so with I counted them concentration of aren't aware that cover the concentration of majority among the same thing all right so if I want to help with the but I don't mind this is going to be concentration times along the concentration we know in the flask is . 1 moles per liter and we said we have 100 ml that solution I said began with the volume would be . 1 0 0 litres 100 million years right and therefore this comes out to be its entry figures comes out to meet 3 times 10 to the negative 2 most I junior mind so this is where I started with this is the amount of the number of moles of that's there to begin with now I want calculate my initial number of moles of hydroxide How much hydroxide and I had 30 ml OK so I have once again concentration tons volume so I know that I have . 1 0 walls Khaleda that's the concentration of my trend I added 30 ml the leaders makes . 0 3 leaders and can leaders and leaders will cancel out and this gives me 3 times 10 to the negative 3 malls of hydroxide the secular everybody so what we calculated is before we had before any reaction took place we calculated the matter had only I had an amount had dropped that I had no remember this is an acid this reaction between a strong acid and a strong base and we know that the net equation is where the hydroxide Antonio reacts with hydroxide to give me liquid water so this fall reaction before any reaction to place I just calculated that I have 1 times 10 to the negative too moles of drawing em and I have 3 times 10 to the natives 3 malls of hydroxyl is good everybody so this is where stock before any reaction to place a cap the malls in the flask and calculated the walls of the 30 ml of these that I added to to the flask again so now they would react with each other so after reaction such nuisances documented problems are right and that this is a limiting reagent problems which is limiting which is success can everything that hydroxide is limiting its unless amount alright so that means of limiting when the reactor is complete and would end up with 0 of that and divisive tractors from that I will have 7 times 10 to the native 3 moles where this says lamenting and this is excess when only concern which is falling water and we know what it is not affect the pH all right and and sell and it's an excess amount it's a solvent so we're not concerned how much water is being produced will just interested in how much acid all the this consumed because it's limited and so will let go away is the excess assets so when that when you have to million as a warning that solution all the bases consumer and all we're left with is high during my tonight to figure out what is to remind concentration because of our couple peach my ultimate goal is to cut the pH so it I want calculate the during concentrations Simon saying I join you mind concentration and this is the excess that's left over from are right and what is the definition of concentration it's always malls
divided by volume we just happen the malls which is 7 times 10 to the 1983 notes now what is the volume remember the reason that we cannot allow this in terms of malls is because of all the keeps changing I started with 100 million years I had 30 ml of days so at that point where is my volume now 130 Tennessee so I I have theirs and divide by the volume which is 130 ml or . 1 3 0 leaders right so now that works out to . 0 5 3 8 smaller so I want you to keep in mind these problems of lots of things are going on out there it is possible that there is based we're having a reaction going on utilization taking place and then we are left with what's left over in U.S. can handle problems of this type now because we've done so many complicated problems now you have to be able to bring all these multiple ideas together and solve this problem and you can do it because you already have all the tools to do it again so now that would be the hydro my concentration that solution how to account the pH take a negative lot of that and if you take the negative log of that the key to the solution comes out to be 1 . 2 6 9 so to begin with the pH was 1 we at head of the strong base 30 ml and I can see the pH went out because some of them I don't mind has been consumed city of Les Hunter reminded solution pH goes out OK so it turns out that you can't calculated in this plot we calculated that we we figured out what the pH is to begin with so we agree on this point we have 30 ml you can figure that out and home knew that there would appear to be when 50 all right and then you should be able to figure out as you add incrementally you can figure out what the future that solution our right now and look at what happens at the equivalent points of the 3rd scenario is that the equivalence .period for stood geometry .period now this is when they have both neutralized each other so what you need to know is that the equivalent .period the malls of high junior mind OK should we the moles of hydroxide all right and so on we know that sequels and all will be there for any policy times we so the all acid that you had said it would be the concentration of H 3 last times the volume L the asset should equal call the concentration of hydroxide times the volume of hydroxide that Senate so you can see that if this is . 1 0 malls print media and we started with 100 ml let's say we know that on the other hand and this is 1 of the most per what this volume to be see so that means you know that start with 100 milliliters of . 1 Moeller beat Seattle wide is the volume of any words that you need to have that the dead 100 ml itself so this is what you calculate you have to figure out so usually you know that you wanted to calculate the volume of hydroxide that needs to be added that would be the concentration of high joining 9 times the volume of the High junior mind divided by by the concentration of hydroxide the silver strong acids strongly you can actually calculated you know the concentration of the Analects no other bodily and like you know the concentration of a tight encountered how much volume need to add and we know that we had 100 ml of the base truthfully completely neutralized when it's completely neutralized what is the pH pH should equal because all we have there is just water and salt and therefore when the 4 strong message strong bases when the 7 we now it's neutralized and that is geometry .period or the equivalent .period no 1 happens to be we ever had in excess of appearing so let's see now we have hit equalizer .period now wouldn't it In excess sold out for the scenario is pH after 2 . 205 200 . 0 5 milliliters of these is added as a literary rights and now we've gone beyond that recalls .period and now we have excess bases are right so so I want to start by asking you is what is the total volume of that solution when we're at the coolers .period members said that the cost by about 100 ml of based so what is the total volume at the equivalence .period To help so we know the total volume at the close .period I am writing to fast now and you can read whatever writing let me know said total volume at equivalent .period would be 200 ml right so where is the volume of excess hydroxide they receiving 200 . 4 5 ml minus 200 ml which is . 0 5 ml rights said that's the volume of the excess hydroxide that we figured out OK so now buy 1 of the with the pH of the solution is trying to figure out how many Malta in the . 5 0 because there but only amount was consumed in neutralized so the only extra hydroxide that you have in there is . 0 5 ml so what is the of that arrange so memory moles of excess hydroxide is always Malta's white concentration at times volume but the concentration of this is . 1 0 multiple leader times the volume now would be . 0 5 divided by a thousand liters erect signed it's . 0 5 ml at to convert that to leaders and so did you work this out this comes out to be 5 times 10 to the negative 5 Oh actually tend and 6 all right so I cannot win the molds of excess you can see that I now have because I'm subtracting these 2 numbers I 1 6 number and carried over one-sixth the number of days so this is the amount of excess number of malls so now because the volume changed I knew I had it .period of anyway to figure out the malls but now my total volume as well 200 . 0 5 pc that so that when happened concentration I figure Texas hydroxide the malls and therefore the ionic calculates the amount of concentration of excess hydroxide
beside the 5 times to the native 6 moles divided by the new volume which is . 2 0 to 100 . 4 5 leaders the I couldn't convert the total volume is not 200 . 0 5 ml conveyed that to leaders and therefore this comes out to be 2 .period itself tend to the negative 5 molar now reminded that said this is a once in a big number and therefore this outcome should be 1 single figure but what I'm doing and I don't want artificially inflated its numbers carrying despite if you divide by 2 you up to 2 . 5 right and so on understand character this number should strictly be a 160 nomination rounded up to 3 but if I can a where you can see that artificially inflating the numbers so I'm putting that subscript 5 to remind me that is carried number over the last understand well enough to 168 all right yes because you medical is .period of 100 ml of this and we have 100 ml of the other right and because when you have equal walls of massive invasive that's the calculation that we did here you see that at the close .period recounted that have 100 million of base so that it is 200 milliliters of this said now that I have hydroxide I think outplayed Hydro we know that kW divided by hydroxide which is 1 times strengthening the 14 divided by 2 . 5 times to the negative file which gives me for . 0 times 10 to the negative 10 smaller all right so again and this time to 266 my results should be 1 single thing never I take the pH of that that comes out to be 9 . 4 the
presence in our country the pH Kaplan pH corresponding to that little excess of hydroxide that I added beyond the pool .period so and that's what you think about the age of any point in the titration right next to us with a look that weak acid strong titration
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