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How do you calculate the average titration ?

the results are as followed:

burette readings/cm cube rough 1 2 3
at end of titration 36.8 44.7 46.2 46.2
at start of titration 0.0 0.0 0.0 0.0
volume of HCL used/ cm cube 36.8 44.7 46.2 46.2

average titration: v/cm cube of HCL = 25.0cm cube of NaOH

i tried adding all the results i had

36.8+ 44.7+ 46.2 + 46.2= 173.9/4=43.475=43.5cm cube but when my teacher corrected it she crossed out the 36.8 and 44.7 and places and X on the answer i got (43.5cm cube)

what did i do wrong? what can i correct my mistake? pleasure help & thank you in advance

Reply 1

charco

Study Forum Helper

Original post by Shordaay

the results are as followed:

burette readings/cm cube rough 1 2 3
at end of titration 36.8 44.7 46.2 46.2
at start of titration 0.0 0.0 0.0 0.0
volume of HCL used/ cm cube 36.8 44.7 46.2 46.2

average titration: v/cm cube of HCL = 25.0cm cube of NaOH
i tried adding all the results i had

36.8+ 44.7+ 46.2 + 46.2= 173.9/4=43.475=43.5cm cube but when my teacher corrected it she crossed out the 36.8 and 44.7 and places and X on the answer i got (43.5cm cube)

what did i do wrong? what can i correct my mistake? pleasure help & thank you in advance

In titration you use the average of the CONCORDANT results (the ones within 0.1 ml of each other).

Your concordant results are 46.2 & 46.2, the average of which is ... 46.2 ml

Reply 2

Shordaay

so if i add the both 46.2 and got 92.4 and divided daht by 4 and got 23.1 is daht still wrong?

Reply 3

TiTo20

Original post by Shordaay

so if i add the both 46.2 and got 92.4 and divided daht by 4 and got 23.1 is daht still wrong?

Yes, because you have only used two of your results adds together, you divide by two to get your average.

Think about it as an equation:

(All of your concordant results added together) / (the number of concordant results used).

This was posted from The Student Room's iPhone/iPad App

Reply 4

Shordaay

i did it over and i add the for results i got and i divided it by 2 and i got 36.8+ 44.7+ 46.2 + 46.2= 173.9/2=86.95... is it correct nw?

Reply 5

Shordaay

could someone explain to me wat i should do cause im really confused here

Reply 6

Shordaay

i tried adding all the results i had

36.8+ 44.7+ 46.2 + 46.2= 173.9/4=43.475=43.5cm cube but when my teacher corrected it she crossed out the 36.8 and 44.7 and places and X on the answer i got (43.5cm cube)

i dont know why she crossed out the 36.8 and 44.7 and only left the 46.2 and 46.2

Reply 7

That Bearded Man

You need CONCORDANT results, i.e answers within 0.1 of each other. This proves accuracy.

You need the average of your two concordant results. So, 46.2 is reasonable.

What did you get for your rough?

Reply 8

That Bearded Man

46.2 + 46.2 / 2 = 46.2

thank you

Original post by That Bearded Man

Hi so I am doing a titration task in school and I am just curious if you had multiple concordant results so multiple pairs, sometimes three in a row or even all your results are concordant how would you calculate these?

i.e.

(46.2,46.2,46.2 ) or (35.5, 35.5, 46.2, 46.2) (35.6, 35.7, 35.8 etc) or even (35.5, 35.5, 35.6, 35.6)

Reply 11

Pigster

35.5, 35.5, 46.2, 46.2 would never happen... you'd have got 35.5 then 35.5 and then stopped as you had two concordant results. Similarly the other examples.

35.5, 35.7, 46.2, 46.2 would not happen - you'd have to conclude that the first two were pretty damn close, but then you got 46.2 which is soooo different something bad must have happened, most likely contamination. Another 46.2 would confirm something bad happened.

35.6, 35.8 and then 35.7 could happen, since the first two are not concordant. The third result would make all three concordant and you'd average all three -> 35.7

I'd have just created a new thread, if I were you. But nice trawling through the archives.