00:01
Okay, so here we have a reaction between edta and calcium 2 plus, and so edta works by keyulating different ions, and so it'll make an edta calcium complex, and so this is just a one -to -one reaction.
00:19
So we have 30 milliliters of solution with calcium ions being titrated, and so we know we have 0 .015 molar edta to reach the equivalence point, the titration of a blank required 2 .5 milliliters of the same edt, same edta to reach the equivalence point.
00:56
So first we want to know the moles of edta that reacted with the blank sample.
01:02
And so how we find the moles of edta is we can take the concentration and multiply it by the volume that we used, which is 2 .5 milliliters.
01:11
But in order to multiply it by the volume used, we need to make sure that the units will cancel out so we can change liters into milliliters by dividing by 1 ,000.
01:21
So then when we multiply by 2 .5, we're only left with moles of edta.
01:28
So here, 0 .0150 times 2 .5 divided by 1 ,000, is 3 .75 times 10 to the negative 5 molar.
01:57
Now b, we want to determine the volume of edta that reacted with the anillate, but not the blank.
02:05
And so we know that we used 37 .65 to reach the equivalence of the regular sample, and 2 .5 to react with the blank.
02:16
So if we subtract out what reacted with the blank, that's going to be the amount that truly reacted with the analyte.
02:23
So 37 .65 minus 2 .5 is 35 .15 mililiters.
02:38
And then lastly, we want to calculate the molarity of the calcium ions in solution...