Question

A person's blood alcohol (C2H5OH) level can be determined by titrating a sample of blood pressure with a potassium dichromat solution. The balanced equation is 16 H + 2Cr2O7 + C2H5OH= 4Cr + 2CO2 + 11H20 a) identify the reducing and oxidizing agents in this reaction. b) In the United States, a blood alcohol content > 0.08% is legal grounds for DUI or DWI charge if a person to titrate 29.00 g of plasma taken from a suspected drunk driver. What is this person's blood alcohol content and are they legally under the influence?

Answer 1

First, define:

Reduction = species that GAINS electrons

Oxidation = process in which a specie will LOSS electrons

Reducing agent = The species that favors reduction, i.e. it will oxidize in order to reduce another species

Oxidizing agent = The species that favors oxidation, i.e. it will reduce in order to oxidise another species

16 H + 2Cr2O7 + C2H5OH= 4Cr + 2CO2 + 11H20

Cr goes from

2Cr + 7O = 0

2Cr + 7(-2) = 0

Cr = +7

to

Cr 0 in Cr(s)

then, it gains 7 electrons, it is reduced

now...

C2H5OH and 2CO2

C goes from -2 in alcohol to

+4 in CO2

it gets oxidized

so,

Cr2O7 --> oxidizing species, contains reduced species

C2H5OH--> reducing species, contains oxidized species

b)

0.08 % = 0.0008 g per g

29 g of plasma -->

mass of alcohol --> 0.0008 *29 = 0.0232 g of alcohol = 23.2 mg is the max amount permissible in the sample

is mass is greter than this, then it is driving under influence