A person breathes in one hour 400 L air at the temperature 25 degrees Celsius an

Question

A person breathes in one hour 400 L air at the temperature 25 degrees Celsius and at 1 atm pressure. This air contains 21% O2, 2% H2O and 77% N2. During the same period, the person exhales 438 L of air at the temperature of 37 degrees Celsius. and if the pressure is still 1 atm. This exhaled air contains 15% O2 and 6% H2O and N2 and some CO2.

The amount of substance of N2, inhaled, is the same as the amount of substance of N2 exhaled.

(A) Calculate the amount of N2 inhaled.
(B) Calculate the volume of the inhaled amount of substance in a pure state N2 at 37 degrees celsius. and the pressure is 1 atm.
(C) Calculate the breath content of N 2, expressed in percentage
(D) Calculate percentage of CO2 in exhaled air

Explanation / Answer

a)

N2 inhaled:

PV = nRT

P-N2 = 1 at* 0.77 = 0.77 atm

n = PV/(RT) = 0.77*400/(0.082*298) = 12.6043 mol of N2

mass = mol*MW = 12.6043*28 = 352.9204 g of N2

b)

volume of N2 at 37ÇC

Apply:

PV = nRT

V = nRT/P

V = (12.6043)(0.082)(37+273)/(1) = 320.4013 L of N2

c)

N2 in %

% N2 = Volume of N2 / Total V = 320.4013 / 438 *100 = 73.150 % is N2

d)

CO2 exhaled

Total % = 15% O" + 6% H2O + 73.150% N2 + x CO2 = 100

CO2 = (100-15-6-73.150)= 5.85% is CO2

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