3. The potassium dichromate reaction was long used as the basis for breath-alcoh

Question

3. The potassium dichromate reaction was long used as the basis for breath-alcohol testing 2K2Cr207 + 3CHcCH2OH + 8H2SO4 2Cr2(S04)3 + 2K2S04 + 3CH3COOH a. (2 pts) What type of reaction is this? b. (2 pts) What color is the reaction result? reen c. (4 pts) Two chemical laws govern this reaction: one that allows the testing of breath to stand in for the testing of blood, and one that allows us to consider the color produced as an indicator of the amount of alcohol present. Name the two laws and explain how each applies.

Explanation / Answer

a)

This is a redox reaction, since ther eis oxidation and reduction between species

b,

the color of ions involved:

cr2O7-2 = orange

Cr+3 = green

therefore, it goes from orange color to green color as Cr+3 is produced

c.

1st reaction:

alcohol can be used in order to measure how much acid is produced as alcohol is oxidized in the breathanalyzer.,

2nd reaction

the change in color will allow us to understan thtat the orange solution ( not much alcohol content present) will convert to green solution if there is plenty of alcohol present

this is Lechatelier principle, if tere is alcohol + Cr2O7-2, then the solution must produce Cr+3 ion (green)

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