Question

7. A human burns 2.5×106 calories per day. At normal body temperature, the heat of vaporization of water is 574 cal/g. a. How many liters of water must a human sweat to remove the heat energy? b. The calculation in (a) is not correct for explaining sweating processes, especially as humans do not sweat as much as you calculated in (a). Why? What was neglected? 8. Alcohol is oxidized in the liver: NAD+ + Ethanol → NADH + Acetaldehyde + H+ Use the Appendix in the textbook to calculate HRXN for this process and then calculate how much energy is released or absorbed when you drink a 50 mL martini, which has ~35% ethanol.

Answer 1

7. a.

A human burns calories per day. At normal body temperature, the heat of vaporization of water is 574 cal/g. Number of grams of water must a human sweat in a day to remove the heat energy

Assuming the density of water to be 1.0 g/mL, the volume of water must a human sweat in a day to remove the heat energy

Convert the volume in L.

To two significant figures the answer is 4.4 L.

b.

At normal body temperature, the heat of vaporization of water is 574 cal/g. This is true for pure water not for sweat as sweat is saturated with various salts.

Also sweating processes is not the only process by which body loses heat. There is heat exchange between body and air. When hot human body comes in contact with cold air, some heat is transferred from body to air.

Also, when we take bath with cold water, heat is lost.