Co formaldehyde) d. Cr in Cro,2 e. Mn in Mn O, f. I in 10 g. Cl in CIO- h. Fe in

Question

Co formaldehyde) d. Cr in Cro,2 e. Mn in Mn O, f. I in 10 g. Cl in CIO- h. Fe in Fe,o 2. For the reaction, answer the questions below: (2 points each) 2 cro,-2 + 3 C2H5OH (ethanol) + 16 H' 4 Cr.. 3 CH,CO,H (acetic acid) + 11 H2O a. What is the oxidation number of Cr in Cr20,2? b. What is the oxidation number of C in C2HsOH? c. What species is oxidized? d. What species is reduced? e. How many electrons are transferred in this reaction? f. What is the oxidizing agent? This reaction was the chemistry behind the first "Breathalyzer' test. Ingested ethanol n s way into the lungs via the circulatory/respiratory systems where some of it is exhale llected. The alcohol reacts with the yellow-orange dichromate ion and the resulting color is measured and blood levels estimated. Neat isn't it!)

Explanation / Answer

the reaction is 2 Cr2O7-2 + 3C2H5OH +16H+ -----------> + 4Cr+3 + 3CH3COOH +11H2O

a) the oxidation state of Cr in dichromate is +6

the oxidation state of O is -2

Let x be the oxidation state of Cr

then 2x + 7(-2) = -2 ,

solving x = +6

b)oxidation state of C in C2H5OH

oxidation state of O = -2 and H = +1

Let Oxidation state of C be x

2x +6(+1) +1(-2) = 0

hence x = -2

oxidation state of C in C2H5OH is -2

c)The species that is oxidised is C2H5OH .

Ethanol is oxidised to ethanoic acid(acetic acid)

d) the species that is reduced is dichromate(Cr2O7-2) . It is reduced to Cr+3

e) the number of electrons transferred are 6.

As 2 Cr in +6 oxidation state are reduced to Cr in +3 oxidation state, the electrons gained By 2 Cr atoms = 2 x 3 = 6electrons.

f) the oxidizing agent is dichromate(Cr2O7-2)  

The oxidising agent is the one that is reduced.

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