Alcohol levels in blood can be determined by a redox titration with potassium dichromate according to the balanced equation:

C2H5OH(aq) +2Cr2O7-2 (aq) + 16H+(aq)---> 2CO2 (g) + 4 Cr3+ (aq) + 11H2O (l)
What is the blood alcohol level in mass perecent if 8.76 mL of 0.04988 M K2Cr2O7 is required for titration of a 10.0002 g sample of blood?

1 answer

moles Cr2O7^-2 = M x L = ??
Convert mole Cr2O7^-2 to moles C2H5OH using the coefficients in the balanced equation. That will be
moles Cr2O7^-2 x (1 mole C2H5OH/2 moles Cr2O7^-2) = ??moles x (1/2) = xx moles C2H5OH.
g C2H5OH = moles C2H5OH x molar mass C2H5OH.
%C2H5OH = (g C2H5OH/mass sample)*100 = ??