WCLN - Precipitation Titration Calculations - Chemistry

Using data from the titration of a chloride solution with silver nitrate, the steps used in calculating the concentration of chloride are explained. http://www.BCLearningNetwork.com. 0:00here will be given some data from a 0:05titration and ask to use this data to 0:08calculate the concentration of anion in 0:10a sample we'll start by looking at how 0:13we handle titration calculations in 0:15general titration calculations in cam 12 0:19involved the reaction between two 0:21reactants which will call a and B here 0:23in the center of all titration 0:26calculations are the moles of reactants 0:28a and the moles of reactants be we 0:31represent number of moles and chemistry 0:33by the letter and reacting a represents 0:37the reactant that were given enough 0:39information to find the number of moles 0:41of to convert moles of a 2 moles of B we 0:45always use the mole ratio or coefficient 0:48ratio of b2a in the balanced equation 0:51for the titration reaction the 0:54information were given about a could be 0:56the molar concentration of a represented 0:59by the letter C and the volume of a in 1:02leaders represented by the letter B or 1:05it could be the massive a and grams 1:07represented by the letter M whatever 1:11were given step one of a titration 1:13calculation is to convert what were 1:15given two moles of reactants a or na 1:19step 2 of any titration calculation is 1:23to convert moles of reactants a 2 moles 1:26of reactants be this is done using the 1:29mole ratio or coefficient ratio of b2a 1:32in the balanced equation we could be 1:35asked one of three different things for 1:37reactant B we could be given the volume 1:40of B and asked to find its molar 1:42concentration CB we could be given the 1:46concentration of B and asked to find its 1:49volume bb or we could be asked to find 1:52the massive be in Grand step 3 and any 1:56titration calculation is to convert 1:59moles of B to whatever were asked for 2:01concentration of B volume of be more 2:04massive be so here is a generic diagram 2:08that outlines the possible steps to take 2:10in most titration calculation problems 2:13remember the first step is always to 2:16find moles of what we can 2:18let's do an example precipitation 2:22titration question a 50 milliliter 2:24sample of a solution known to contain 2:26fluoride her cl- science is titrated 2:30with point 100 molar agno3 solution a 2:34small amount of sodium chromate is added 2:36to the sample as an indicator three 2:39separate trials are done we're asked to 2:41find the concentration of cl minus in 2:44the original sample the results are 2:47recorded in a table like this 2:49the first thing we need to do is 2:51calculate the volume of a gno three 2:53solution used in each trial we do that 2:57by subtracting the initial be reading 2:59from the final be rereading so in trial 3:02one its 4.46 minus point 95 which is 3:073.51 milliliters for trial to the volume 3:12is 7.65 minus 4.45 which is 3.20 3:18milliliters and in trial three the 3:21volume used his 10.8 7-7 points65 which 3:27is 3.2 two milliliters taking a look at 3:31these three results we see that the 3:33volume used in trial 13.5 one 3:36milliliters is considerably higher than 3:393.20 and 3.22 used in trials two and 3:44three respectively for that reason we 3:47just discard the value of 3.51 we 3:51calculate the best average volume of AGN 3:5403 by taking 3.20 plus 3.22 and dividing 3:59by 2 which gives us 3.21 milliliters 4:03will make a note of the average volume 4:06of 3.21 milliliters appear in the table 4:10will convert the three-point 21 4:12milliliters 2.00 321 leaders at this 4:17point let's dissociate the AGM three 4:20here and we get a G+ and no.3 minus and 4:25will dissociate 4:26the AGM three here also giving us a G+ 4:31and no.3 minus the nitrate I and no.3 4:34minus a spectator I it does not form any 4:37precipitates will just discard it so we 4:41can simply say that the concentration of 4:43AG plus his point 100 molar and the 4:48volume of a G+ solution used is equal to 4:51point zero zero 321 leaders so we have 4:55all the information we need up here now 4:57we'll just rearrange it a bit so it 5:00looks like this we have the 5:02concentration of a G+ and the volume of 5:05a G+ here and the volume of co- here at 5:10this point will convert the 50