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 estimatethe percentage of Calories that comes from thealcohol, consider the following questions. (a) Write abalanced chemical equation for the reaction of ethanol,C2H5OH, with oxygen to make carbon dioxide andwater. (b) Use enthalpies of formation in Appendix Cto determine ΔH for this reaction. (c) If 4.2% of the totalvolume is ethanol and the density of ethanol is0.789 g/mL, what mass of ethanol does a 12-oz servingof light beer contain? (d) How many Calories arereleased by the metabolism of ethanol, the reaction frompart (a)? (e) What percentage of the 110 Calories comesfrom the ethanol?
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
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
part (a)? (e) What percentage of the 110 Calories comes
from the ethanol?
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