Titrations, URGENT

I have to answer some questions regarding the titration practical which I have really no clue how to answer:

why do we make a solution of a similar concentration as the unknown one?

why do we need to rinse the beaker two or three times with small amounts rather than once with a bigger amount)?

why do we pipette the solution from a beaker rather than directly from the volumetric flask?

Why do we leave the pipette to empty under gravity?

any help is appreciated!

Reply 1

Pavliseb

I'd say 1) so the consumption of the volumetric solution isn't too big or too small
2) It could be possible that not the whole beaker would be "cleaned" and you would waste too much sample
3) Because you could contaminate the sample

Reply 2

Pigster

20

You only want them of similar conc. if it is a 1:1 reaction.
Rinsing may leave 10% of the contaminant behind with little washes, but 10% or 10% of 10% would be better than one thorough wash, which might only leave 1% behind.
The pipette might not be long enough to reach the chemical in the vol. flask (also contamination)
So that you aren't tempted to 'blow out'.

Reply 3

okelydokely

OP

8

Original post by Pigster

You only want them of similar conc. if it is a 1:1 reaction.
Rinsing may leave 10% of the contaminant behind with little washes, but 10% or 10% of 10% would be better than one thorough wash, which might only leave 1% behind.
The pipette might not be long enough to reach the chemical in the vol. flask (also contamination)
So that you aren't tempted to 'blow out'.

thank you so much could you explain what you mean by 'blow out'?

OP

thank you so much

OP

Original post by Pavliseb

I'd say 1) so the consumption of the volumetric solution isn't too big or too small
2) It could be possible that not the whole beaker would be "cleaned" and you would waste too much sample
3) Because you could contaminate the sample

thank you!!

Reply 6

Pigster

20