2. ** (Student HW) Breathing uses chemical and mechanical processes to bring oxygen to every cell of the body and to get rid of carbon dioxide. Our body needs oxygen to obtain energy to fuel all our living processes. Carbon dioxide is a waste product of that process. The following table gives the measured pressures of the major gases in both inhaled and exhaled air.

	Inhaled Air / mmHg	Exhaled Air / mmHg
	597	568
	513	116
	0.3	28
	5	48
	8	8

 

Calculate and compare relative mole fractions of each gas in inhaled vs exhaled air.

* Nitrogen is an inert gas with regard to inhalation / exhalation, that is, the body does not do anything with is. Since water is added to the exhaled air the percentage of each inert component will have to go down in exhaled air

 

An adult takes roughly 12 breaths each minute, inhalingapproximately 500mL with each breath. Oxygen and carbon dioxide areexchanged in the lungs. The amount of nitrogen exhaled equals theamount inhaled, and the mole fraction of nitrogen in the exhaledair is 0.75. The exhaled air is saturated with water vapor at bodytemperature, 37

In respiration, air is inhaled into the lungs, which provide a large surface area for transport of oxygen, carbon dioxide, and water to or from the blood. The transported oxygen is delivered to body cells where it oxidizes glucose and fats from food to produce carbon dioxide, water, and thermal energy. The carbon dioxide and water are transported from the cells to the blood and back to the lungs, from which they are exhaled. The exhaled gas is at body temperature and saturated with water, some produced in the glucose and fat oxidation and some additionally drawn from moist lung tissue. Other water-containing streams— food, water, perspiration, and excreted waste streams—maintain the body’s level of hydration.

Suppose an individual inhales air at 20°C and 20% relative humidity, and 25% of the inhaled oxygen is consumed in the glucose oxidation reaction. (Under certain conditions, it is reasonable to neglect the oxidation of fats.) A flowchart of the respiration–metabolism process is shown below. The water in the exhaled gas equals the inhaled water plus the water produced by glucose oxidation plus additional water drawn from the lungs. Qm represents only the heat transferred to or from the body as a consequence of the phenomena just described; not shown are heat and work transferred due to other bodily processes.

(a) Assume a basis of 1 mol bone-dry air (plus the water that goes with it) inhaled at 20°C. Draw and fully label a flowchart of the metabolic process, considering only breathing and glucose oxidation as components of the process. You don’t need to label the streams between the two units, since this problem will not require determining their masses or compositions. Do a degree-of-freedom analysis of the overall system.

(b) Suppose all of the water and CO2 produced from the glucose oxidation are transported to the lungs and exhaled, and calculate the masses of all components of all labeled streams.

(c) If the individual inhales an average of 500 mL of air per breath and takes 12 breaths per minute, how much water (fluid ounces) must she drink per day to make up for the water she loses by breathing?

(d) Returning to the original basis, estimate the heat (kJ) transferred to or from the body as a consequence of breathing and glucose oxidation, assuming that the glucose is oxidized at 37°C and at that temperature ΔHc= -2816 kJ/mol: