One of the best-selling light, or low-calorie, beers is 4.2%
alcohol by volume and a 12-oz serving contains 110 Calories;
remember: 1 Calorie = 1000 cal = 1 kcal. To estimate
the percentage of Calories that comes from the
alcohol, consider the following questions. (a) Write a
balanced chemical equation for the reaction of ethanol,
C2H5OH, with oxygen to make carbon dioxide and
water. (b) Use enthalpies of formation in Appendix C
to determine ΔH for this reaction. (c) If 4.2% of the total
volume is ethanol and the density of ethanol is
0.789 g/mL, what mass of ethanol does a 12-oz serving
of light beer contain? (d) How many Calories are
released by the metabolism of ethanol, the reaction from
part (a)? (e) What percentage of the 110 Calories comes
from the ethanol?