Titration - Are my steps right (1 Viewer)

[Lordsion]

I have to do a 1 part vinegar to 4 part water dilution. (1 in 5 dilution)

So to dilute the vinegar i just collect 50 ml vinegar and add 200 ml water.

Then place the diluted vinegar into the burette and do a titration on the NaOH (25ml)


So i dont have to work out the concentration of vinegar? (NaOH concentration given)

 

[dan.121212]

the whole point of the titration is to find the concentration of acetic acid in vinegar, is it not?

there fore u titrate diluted solution roughly, then 3 times within 0.1mL, then work out concentration of acetic acid in that diluted mixture, then use that to work out the concentration of acetic acid in the undiluted (normal) vinegar---> in g/L, mol/L, and as %

 

[Lordsion]

the whole point of the titration is to find the concentration of acetic acid in vinegar, is it not?

there fore u titrate diluted solution roughly, then 3 times within 0.1mL, then work out concentration of acetic acid in that diluted mixture, then use that to work out the concentration of acetic acid in the undiluted (normal) vinegar---> in g/L, mol/L, and as %

This will sound dumb, but 0.10 Mol is the same as 0.100 Mol right?

 

[dan.121212]

short answer: no

-------DO NOT READ ON IF YOU STRUGGLE WITH THE IDEA OF SIGNIFICANT FIGURES-------

...however
0.10 mol is to two significant figures

WHILE

0.100 mol is to three significant figures

it's all bout accuracy - if a question gives u all info to 3 significant figures, ur answer is to 3 significant figures

similarly, if a question gives u all info to 2 significant figures, put ur answer is to 2 significant figures

Re: significant figures, from Andrew Harvey's notes:
"The quantity 3.00 has three significant figures, that being the „3‟, the „0‟ and the „0‟. These three digits define the accuracy of a quantity. For example the quantity 3.00 specifies that the tenths and hundredths of the quantity are zero. This is different to the quantity 3 which means that we only know that the units are 3, we don‟t know the tenths or the hundredths. And so 3.00 has three significant figures and 3 has one, this means that 3.00 is much more accurate"

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[Undermyskin]

Hey, I have Andrew Harvey's notes as well but who is he?

Agree, the whole point is to find the concentration of CH3COOH in that sample of vinegar.

Concisely, no. You prove this, why did you say 'yes'? In case of 0.10, the accurate answer must be given up to +-0.01 while for 0.100, up to +-0.001.

When looking at s.f., follow that of the given info with same measuring devices (Whether g or kg, etc.) However, if the given info have different s.f., give your answer following that of the LESS accurate one.

 

[dan.121212]

Hey, I have Andrew Harvey's notes as well but who is he?

Agree, the whole point is to find the concentration of CH3COOH in that sample of vinegar.

Concisely, no. You prove this, why did you say 'yes'? In case of 0.10, the accurate answer must be given up to +-0.01 while for 0.100, up to +-0.001.

When looking at s.f., follow that of the given info with same measuring devices (Whether g or kg, etc.) However, if the given info have different s.f., give your answer following that of the LESS accurate one.

i answered yes, cause i didnt wanna confuse people - some people (who don't do 4U maths like us, jks) might not grasp the concept, and if i said 'no' theyd be like 'so wat do i punch into the calculator?' - in terms of punching into calculator, they are the same, its just the S.F. u put ur answer to, so yeh ive hcanged it to 'no' now

in terms of 'less accurate one' as 'undermyskin' mentioned,. yeh that's correct - was gonna include that in my original post, but thought it'd be a bit much but yeh - relevant

BTW Andrew Harvey is a 2007 HSC student, who made notes for Chemistry and Physics (and possible other subjects)

 

[brenton1987]

I have to do a 1 part vinegar to 4 part water dilution. (1 in 5 dilution)

So to dilute the vinegar i just collect 50 ml vinegar and add 200 ml water.

That is a very bad assumption to make. There are numerous compounds that dont dilute like that at all.

You should be taking your 50 mL solution and diluting it to a 250 mL solution.