A tricky question ???? + DILUTION HELP!!! PLEASE...

[aronno]

the amount of ethanol is determined by colorimetry. A 0.50ml sample of wine is diluted to 90ml. 10.1ml of 0.100M acidified potassium dichromate is added and the resulting solution is warmed at 50 degrees for 15mins

Q.1. why is the solution held at 50 degrees for 15mins?

Q.2 it was found that the conc. of the dichromate in the test solution is found to be 0.0028M as well as having an absorbance of 0.010. Now calaculate the ammount i mol of the ethanol that reacted with dichromate in the original test solution.

Q.3 calc. the mass of ethanol per mL present in the original sample of white wine.

THANKS TO ALL!!!!

on another note i suck at dealing with dilutions!!! can anyone give me an explaination on what changes and doesnt. If you know what i mean. like in titrations where a substances is diluted and the aliquots are taken out. HOW DO THEY AFFECT CERTAIN VALUES. e.g the mol or the conc etc. HELP!!! PLEASE. Is there an easy way of tackling questions that involve all the dilutions and aliquots moving etc.
 
THANKS AGAIN!!!

[d0minicz]

for dilution, the number of moles doesnt change but the concentration is reduced

edit: when tackling questions involving dilutions and aliquots being removed etc always note down the factors of dilution/change

eg:  20mL diluted to 200mL = factor of x10

[aronno]

thanks dude!!
now can anyone give me a sample question! like in titrations invovling dilutions.
Oh and the answers to the questions earlier

cheers