laws passed in some states define drunk driver as one who drives with a blood le

Question

laws passed in some states define drunk driver as one who drives with a blood level of 0.10% by mass of higer. the level of alcohol can be detemined by titration bloof plama with potassium dichromate accoridng to the following equation

assume that the only substance that reacts with cr2o7^2- is blod plasma C2H5Oh

(a)how many grams of alcohol are in a sample of blood plasma if 38.94 ml of 0.0723M Cr2O72- is needed to titrated with all alochol sample?

(b)is a person legally drunk if the blood plasma samole has a mass of 50.0 g?

Explanation / Answer

a)

16 H+(aq) + 2 Cr2O72-(aq) + C2H5OH(aq) ----------------> 4 Cr3+(aq) + 2 CO2(g) + 11 H2O(l)

Moles of Cr2O72- = volume x concentration of Cr2O72-

                          = 38.94 x 0.0723 / 1000

                          = 0.002815 mol

Moles of C2H5OH = 1/2 x moles of Cr2O72-

                           = 1/2 x 0.002815

                           = 0.001408 mol

Mass of C2H5OH = moles x molar mass of C2H5OH

                           = 0.001408 x 46.069

Mass of C2H5OH = 0.0648 g

b)

Percent alcohol in blood = mass of C2H5OH/mass of sample x 100%

                                    = (0.0648/50 )x 100%

                                     = 0.130 %

no he is not legally drunk. because it is not 0.10 % < 0.130 %

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