Question

A person inhales air richer in O2 and exhales air richer in CO2 and water vapor. During each hour of sleep, a person exhales a total of 300. L of this CO2-enriched and H2O-enriched air. (a) If the partial pressures of CO2 and H2O in exhaled air are each 37.5 torr at 36.8°C, calculate the masses of CO2 and of H2O exhaled in 1.00 hour of sleep.

CO2

H2O

b) How many grams of body mass does the person lose in about 8 h sleep if all the CO2 and H2O exhaled come from the metabolism of glucose? (Note: 8 h has 1 significant figure, so round your answer to 1 sig. fig.)

Answer 1

From the given total volume,

Number of mols of CO₂ / H2O = PV/RT = (37.5 /760) atm*300 L / 0.0821*(36.8+273) K

= 0.581 mol

Thus mass of CO₂ = (0.581 mol)(44.0 g/mol) = 25.564 g

Mass of H₂O = (0.581 mol)(18 g/mol) = 10.458 g

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b) Mass of CO₂ and H₂O will be lost in 8 hrs = 8(25.564) + 8(10.458) = 288.176 g = 300 g (in 1 sig.fig)

This is the amount lost by glucose = 300 sig.fig.