How do they react?

pivoxa15

How does acidified potassium dichromate, K2Cr2O7 react with ethanol, C2H6O ? What is the resultant product?

And as an aside question what is the difference between acidified potassium dichromate and potassium dichromate?

Gokul43201

pivoxa, this is a standard textbook problem and belongs in the Homework section.

Acidified dichromate is a solution of dicromate mixed with a suitable dilute acid. Acidification increases the oxidation potential of the dichromate ion.

symbolipoint

This helps to verify result of ethanoic or acetic acid:
http://www.outreach.canterbury.ac.nz.../ethanol.shtml

pivoxa15

I've seen this site but what are the half reactions?

For chromium, it's (Cr2O7)2- + 14H+ + 6e- -> 2Cr3+ + 7H2O

For ethanol on the surface it looks like C2H5OH + O2 -> CH3COOOH + H2O
but where is the electron in this half reaction?

Gokul43201

C2H5OH + H2O + ---> CH3COOH + (H+) + (e-)
Balance and premultiply as required to complete.

Alternatively, to your above second reaction, add the third reaction:
H2O ---> O2 + (H+) + (e-) and balance the lot of them.

pivoxa15

The two half reactions are
((Cr2O7)2- + 14H+ + 6e- -> 2Cr3+ + 7H2O ) * 2
C2H5OH + H2O -> CH3COOH + 4(H+) + 4(e-) * 3

Net reaction is:
3C2H5OH + 2(Cr2O7)2- + 16H+ --> 3CH3COOH + 4Cr3+ + 11H2O

The trick was in determing that the product of C2H5OH is CH3COOH. The rest can be done by balancing water, H+ and e-. Are there ways of working out which product will form or do people usually look at tables. FOr predicting complex reactions is the best way to look up in a table? If so is there a large table on the web? I have seen ones in the textbook but many reactions seem to be missing from them.