Textbook Problem

The blond alcohol (C₂H₅OH) level can be determined by titrating a sample of blond plasma with an acidic potassium dichromate solution, resulting in the production of Cr³⁺ (aq) and carbon dioxide. The reaction can be monitored because the dichromate ion (Cr₂O₇²⁻) is orange in solution. and the Cr³⁺ ion is green. 'The unbalanced redox equation is

${\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}{}^{\text{2}+}\left(aq\right)+{\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}\left(aq\right)\to {\text{Cr}}^{3+}\left(aq\right)+{\text{CO}}_{\text{2}}\left(g\right)$

If 31.05 mL of 0.0600 M potassium dichromate solution is required to titrate 30.0 g blood plasma. determine the mass percent of alcohol in the blood.