Reference no: EM13255716

Blood alcohol content (BAC) is often reported in weight-volume percent (w/v%). For example, a BAC of 0.08% corresponds to 0.08 g CH3CH2OH per 100 mL of blood. In Ontario, and the rest of Canada, the maximum legal BAC for fully licensed drivers is 0.08%. Estimates of BAC can be obtained from breath samples using a number of commercially available instruments, including "The Breathalyzer". The original Breathalyzer instrument was based on the following oxidation-reduction reaction.

Balance the equation:

CH3CH2OH(aq) + Cr2O72(aq) acidicsolution-> CH3COOH(aq) + Cr3+(aq) ethyl alcohol (yellow-orange) acetic acid (green)
A Breathalyzer instrument contains two ampules, each of which contains 0.75 mg K2Cr2O7 dissolved in 3 mL of 9 mol L?1 H2SO4(aq). One of the ampules is used as reference. When a person exhales into the tube of the Breathalyzer, the breath is directed into one of the ampules, and ethyl alcohol (CH3CH2OH) in the breath converts Cr2O72? into Cr3+. The instrument compares the colours of the solutions in the two ampules to estimate the blood alcohol content. The estimate of the BAC rests upon the assumption that 2100 mL of air exhaled from the lungs contains the same amount of alcohol as one millilitre of blood.

The Breathalyzer instrument typically tests 52.5 mL of exhaled breath. (a) If the test of such a breath sample yields a reading of 0.08%, what are the partial pressure and mole fraction of CH3CH2OH in the breath of the person who was tested? Assume the atmospheric pressure and temperature are 101 kPa and 21.0 oC, respectively. (b) A BAC of 0.40% is considered the lethal limit for humans (i.e. for a majority of adults, a BAC value of 0.40% causes death). By performing an appropriate calculation, determine whether or not the Breathalyzer instrument, as described above, can be used to measure BAC as high as 0.40%.