2003 paper q 23 (1 Viewer)

[paper cup]

For titrations the first titre is always a rough so for this q you should take the last three and average the figures - which should give a volume of 0.0181. The answer gives it at 0.0183, I don't get it.
This is from success one, the answers, btw

 

[Dreamerish*~]

The last three results are 18.1, 18.2 and 18.1.

18.1 + 18.2 + 18.1 = 54.4

54.4/3 = 18.13* mL

 

[Haku]

yes you should always diregard the first result from titration as errors from unclean or contaminated equipments occur. But it doesn;t really matter which of the rest u choose to use. in this case i used just 18.1 as two tests gave that answer and i think its more reliable and accurate than the rest.

 

[paper cup]

hold on either I can't read or the STA teachers can't count

nope they can't count. Thanks both of you - oh nosadness, it's best to average them because that's what you would do in a writeup, according to my teacher

 

[jarro_2783]

yes you should always diregard the first result from titration as errors from unclean or contaminated equipments occur. But it doesn;t really matter which of the rest u choose to use. in this case i used just 18.1 as two tests gave that answer and i think its more reliable and accurate than the rest.

it's got nothing to do with unclean or contaminated equipment. You are supposed to clean your equipment properly before you do any titration. ie. Clean the burette with whatever you are putting in it, clean the pipette with whatever you are putting in it and clean the flask with distilled water. The rough titration is just to get an idea of where the end point is, you do it quickly and as such you may be off by a few mLs, so for the rest you go quickly to about two mLs before the rough one ended and then go slowly. It's just so you don't have to empty out 25 mLs one drop at a time.