Titration help (1 Viewer)

[Joga Bonito]

Im really confused about how the glassware should be prepared before titration, specifically the preparation of the conical flask.
correct me if im wrong but burette and pipettes are rinsed with the solution that is goig to be placed in them right? and the volumetric flask for the standards solution is washed with distilled water and may be left wet.

now with the conical flask, my textbooks say thatyou should wash the distilled water, and that it MAY BE LEFT WET. BUT; don't we place our primary standard solutions in the conical flasks for titration? so doesn't that mean by having a little bit of water already in the conical flask, if we add our primary standard, the concentration of the solution would be altered, thus making the titration invalid?

its really confusing me, any help appreciated

 

[Aerath]

In the conical flask, we're only after the number of moles of the standard solution. Hence we could have like 200mL of distilled water in the conical flask, but it'd still be the same number of moles of standard solution.

And yes, burettes and pipettes are rinsed with the solution that is going in them.

 

[Joga Bonito]

ohhh...that clears things up, thanks champ

 

[aero135]

wait now i dont get it? WTF .....number of what in the standard?

 

[Aerath]

Sorry, number of moles in the standard solution.

 

[kwabon]

wait now i dont get it? WTF .....number of what in the standard?

adding excess water into the conical flask will not the change the number of moles, but instead will change the concentration, so u can alot of water into the conical flask and will still get a consistent answer assuming you have performed the titration properly.

lol, now you have got me confused, i hope i answered your question.

 

[aero135]

lets just say 200ml is added. THen the base is DILUTED!!! this will affect concentraion. Given volume has increased 'n' has to change...?

 

[annabackwards]

lets just say 200ml is added. THen the base is DILUTED!!! this will affect concentraion. Given volume has increased 'n' has to change...?

n = cV

ie V = n/c

As n stays constant, V is inversely proportional to c, so if move volume is added then the concentration decreases.

 

[Aerath]

lets just say 200ml is added. THen the base is DILUTED!!! this will affect concentraion. Given volume has increased 'n' has to change...?

No it doesn't. I've got 3mL of red paint, and I add 20mL of blue paint, I've still got 3mL of red pain there. Doesn't matter if I add another 400mL of blue paint, there's still 3mL of red paint there.

 

[Aerath]

Sorry Anna, my analogy kicks ass.

 

[annabackwards]

Sorry Anna, my analogy kicks ass.

Hehe, i'd have to agree XD

 

[kwabon]

No it doesn't. I've got 3mL of red paint, and I add 20mL of blue paint, I've still got 3mL of red pain there. Doesn't matter if I add another 400mL of blue paint, there's still 3mL of red paint there.

thats a really good example, where on earth did u come up with that?

 

[Aerath]

I just thought of it?

 

[FoRc]

not really , once u add the blue paint theres no red paint cos its mixed..
(plz dont be wrong)