23. Every year in the US, hundreds of thousands of people are injured or killed

Question

23. Every year in the US, hundreds of thousands of people are injured or killed because of drunk driving, if a police officer suspects that a person is driving drunk, he or she may use a Breath Analyzer Breathalyzer) to detect alcohol (ethanol, CH,0] in the person's breath. The chemistry invoved in the analysis involves an oxidation-reduction reaction between ethanol and acidified potassium dichromate solution. In the presence of ethanol, the orange-yellow dichromate solution turns green. The incomplete redox equation follows. a) Which element is oxidized? b) Which element is reduced? c) The complete, BALANCED REACTION is as follows: How many grams of K,Cr,O, (294.1846 g/mol) are required to react with 10.00 mL of 0.0125 M C,H,O?

Explanation / Answer

23. from equation.

a. element oxidised = carbon(C)

b. element reduced = Chromium(Cr)

c) 3 mol C2H6O = 2 mol K2cr2O7

no of mol of ethanol = 10*0.0125/1000 = 0.000125 mol

no of mol of K2Cr2O7 = 0.000125*2/3 = 8.333*10^-5 mol

Mass of K2Cr2O7 = (8.333*10^-5)*294.1846 = 0.0245 g

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