the ETHANOL CONTENT IN WINE!!!! :<

[aronno]

this is a redox/back titration type question that invovled:
AIM: TO DITERMINE THE CONC. OF ETHANOL IN WINE BY BACK TITRTION!!!

iodine being titrated titrated against a standardised sodium thiosulfate solution

I₂ -> I^-
S₂O₃^2- --> S₄O₆^2-

Then ther excess dichromate can then be ditermined in a two step process. First excess potasssium iodide was added. This is oxidised to iodine.
I^- --> I₂
Cr₂O₇^2- --> Cr³⁺

The alchol content in wine is ethanol (CH₃CH₂OH). Under carefully controlled conditions the ethanol in a sample of wine can be oxidised to ethanal(CH₃CHO) using a acidified potassium dichromate.

MY QUESTION;
what is the effect on the calculated concentration if:
the wine - dichramate mixture was not heated for long enough in the water bath?
The water bath was set at 60 degrees instead of 50 degrees?
An insuffiecient amountof KI was added after heating was complete?
the flasks containing ethanol and acidified dichromate were not stoppered when placed in the water bath?

PLEEEEASE HELP! 

[aronno]

please reply  this is dead urgent
your help will be greatly appreciated!!
PLEEEASE ><><><<><<>

[jackinthepatch]

Well what the hell is the water bath?

Lol, you haven't told us the whole procedure, so I don't really know how to answer.

[paulii]

I dont do chemistry and when readings this im like WTF?

However, i do know all alcohol has 10% pure ethanol in it.

[hard]

whenever i see the word 'titration' i feel like hanging myself.

[jackinthepatch]

The feeling is mutual

[aronno]

MY BAD!!

the method:
1- Fill a 10.0mL pipette with wine and place in a 250mL volumetric flask. Make up to the mark with deionised water and shake to ensure complete mixing.

2- using a 20mL pipette transfer an aliquot of wine to each of the four 250mL conical flasks

3- record the conc. of the potassium dichromate solution. fill the second 20.00mL pipette with the potassium dichromate soltuion and transfer to each of the flsaks containing wine.

4- wearing gloves and using a measuring cylinder, slowly add approximately 10ml of 50% sulfuric acid to each conical flask

5- Stopper each flask loosely and heat them in a water bath (maintained at 50 degrees!!!) for 10 mins.

6- when heating is complete, add an excess of potassium iodide (approx. 2g) to each flask

7-record the conc. of the sodium thiosulfate solution before filling the burrette. titrate the contents of each conical flask with the sodium thiosulfate solution until sol.  changes into a greenish brown colour. When this occurs add 6 drops of starch solution and contiue the titration until the equivalence point which occirs when the blue colour of starch-iodine complex, just appears. leaving a clear, green colour. Record reading on the burette.

SORRY ---MIND BLANK!

[aronno]

MY QUESTION;
what is the effect on the calculated concentration if:
the wine - dichramate mixture was not heated for long enough in the water bath?
The water bath was set at 60 degrees instead of 50 degrees?
An insuffiecient amountof KI was added after heating was complete?
the flasks containing ethanol and acidified dichromate were not stoppered when placed in the water bath?

PLEEEEASE HELP!   

[jackinthepatch]

Hmm I really don't understand the way the prac works lol. Sorry mate, hopefully someone else can help ya.

[Chemkid]

So hang on, you had ethanol in vinegar, which was reacted with Dichromate ions in a redox reaction, then excess iodine was added and titrated with Sodium Thiosulfate? Sounds like a back titration to me We dont do that in the VCE course! Correct me if I'm wrong 

[jackinthepatch]

Yeah we do back titration. But this is a bit weird...I dunno, maybe Mao or TrueTears can help out.

[Chemkid]

Sorry! I meand double back titration ! Of course we do back titrations My bad!

[jackinthepatch]

Lol no worries. I was gonna say, if you didn't know we did back titration then you'd be stuffed! Haha.

[hard]

yer i still don't know what titration means tbh. i haven't done 1 single q at home thus far.

[jackinthepatch]

Lol solid effort