# chem

The chemical method of analysis in determination of the blood alcohol content %BAC is:

K2Cr2O7 + H2SO4 + C2H5OH ---> Cr2(SO4)3 + K2SO4 + CH3COOH + H2O

What are the stoichiometric coefficients for the reaction above?

Cr is reduced from +6 each on the left to +3 each on the right.
C (in C2H5OH) is oxidized from -2 each on the left to zero for each on the right. Draw a line from Cr on the left to Cr on the right. On the left write +12 above the 2Cr (that is +6 each x 2 atoms = +12) and on the right write +6 above the Cr2 (that is +3 each x 2 = +6).
Next, draw a line from C on the left to C on the right. On the left write -4 above the C2 (that is -2 each x 2 = 4) and on the right write 0 (that is 0 each x 2 = 0).
Here is how you finnish.
1. Determine the loss and gain of electrons.
2. Multiply the loss and gain by coefficients that will make the loss equal to the gain. I found 3 and 4 to be the numbers used to multiply to make 12 electrons lost and 12 electrons gained.
3. Multiply those compounds connected with the lines you have drawn by the coefficients used to make the e gain = e lost; i.e., you will multiply one set by 3 and one set by 4.
4. By inspection, balance those atoms not changed by oxidation or reductin.
Post your work if you get stuck. I shall be happy to check your finished equation if you show the intermediate steps that lead to the finished product. I hope this helps.

Thanks for your help. I will post my work if I need more help.

coefficients are 2+8+3 --> 2+2+3+11

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2. 👎 0
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