Question 7 2 pts A breathalyzer is a device used to estimate the blood alcohol c

Question

Question 7 2 pts A breathalyzer is a device used to estimate the blood alcohol content of a suspected drunk driver by measuring the amount of alcohol in one's breath. The fuel cell breathalyzer employs the reaction below: CH3CH2OHgO2g) HC2H3O2(g)+H20(g) When a suspected drunk driver blows his or her breath through the fuel-cell breathalyzer, the device measures the current produced by the reaction and calculates the percent alcohol in the breath. When a suspected drunk driver blows 385 mL of his breath through the fuel-cell breathalyzer, the breathalyzer produces an average of 392 mA of current for 13 s. Assuming a pressure of 1.0 atm and a temperature of 26 °C, what percent (by volume) of the driver's breath is ethanol? (Hint: convert to volume using the ideal gas law) Express your answer as a percentage usi ing three significant figures

Explanation / Answer

faradays first law

equivalent weight of ethanol (E)= Mwt /no of e- exchanged

      = 46/4 = 11.5 g/equiv

W = Zit

Z= E/F

w = (E/F)it

i = current = 0.392 A

w = weight of ethanol = ? grams

t= time taken = 13 s

F = 96500 c

w = (11.5/96500)*0.392*15

    = 0.0007 g

no of mol of ethanol in breathe sample = w/M

             = 0.0007/46 = 1.52*10^-5 mol

volume of ethanol(V) = nRT/P

            = ((1.52*10^-5)*0.0821*(26+273))/1

            = 0.000373 L

            = 0.373 ml

percent alchol in breath = vol.alchol/vol.of breath*100

                 = 0.373/385*100

                 = 0.0969 %

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