Re: How does the oxidation state of chromium in acid' dichromate (VI) change

Dave,
   You are correct in your suspicion that the oxidation state of the 
chromium changes during the reaction.  Chromium (VI) is used for a variety 
of oxidation processes, the most common one bieng the oxidation of secondary 
alcohols to ketones.  In the overall process, acidified CrO3 reacts with an 
alcohol, and the alcohol is oxidized and the chromium is reduced.  The 
alcohol is oxidized to either an aldehyde or a ketone, and the reduced 
chromium species that is formed is the HOCrO2 anion, in which chromium is 
present as Cr(IV).  If you are interested in seeing a step-by-step mechanism 
for this reaction, consult any undergraduate college level organic chemistry 
text, and look for the topic "oxidation of alcohols."   A good web site that 
gives descriptions of this and many other organic reactions is one developed 
by Dr. Linda Sweeting at Towson University: http://www.towson.edu/~sweeting/
orgrxs/reactsum.htm
At this site, go to the link for alcohol reactions, then scroll down until 
you see the chromic acid oxidation.  Click on the reagent to see a further 
description of its properties and uses.