In Pennsylvania, the legal definition of intoxication is a blood alcohol (ethyla

Question

In Pennsylvania, the legal definition of intoxication is a blood alcohol (ethylalcohol, C2H5OH) content normally stated as being higher than 0.1. This actually refers to a blood alchol conent of 0.1% by mass. (there is a good possibility that this will be changed to 0.08% in the near future). The following chemical reaction can be used to establish the alcohol content of a sample.

16H^+1 (+) 2Cr2O7^2- (+) C2H5OH ----> 4Cr^3+ (+) 2CO2 (+) 11 H2O

If a 48.91 gram sample of blood taken from person suspected of "being under the influence" required 48.02 mL of 0.05182 M Cr2O7^2- for a complete reaction, determine if that person was legally intoxicated (use the 0.1 value)

What is the person's blood alcohol content?

Explanation / Answer

Amt. of Cr2O7^2 = 48.02*0.05182 mili. moles = 2.4883 mmoles

thus moles of C2H5OH = 0.5 * cr2o72-

thus wt of C2H5OH in alcohal = 0.5*2.4883* 46.06844 mg =57.316049626 mg

so percent of blood alcohal by mass = 57.316049626*0.1/48.91 = 0.11718677085 percent

hence persons alcohal content is 0.11718677085 by mass.

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