Problem: During a persons typical breathing cycle, the CO2 concentration in the expired air rises to a peak of 4.6% by volume.Calculate the partial pressure of the CO2 in the expired air at its peak, assuming 1 atm pressure and a body temperature of 37oC .

FREE Expert Solution

We are asked to find the partial pressure of CO2 in the expired air assuming 1 atm pressure and a body temperature of 37oC. CO2 has a concentration of 4.6% by volume in the expired air. 


The Partial Pressure of a gas is equal to the pressure multiplied by the mole fraction of gas.

PCO2 = χCO2 ×Patm


We will calculate the partial pressure of CO2 using the following steps:

       Step 1: Calculate the volume of CO2 and air in the solution.
       Step 2: Calculate for the number of moles by using the Ideal Gas equation.
       Step 3: Calculate the mole fraction of CO2.

       Step 4: Calculate the partial pressure of CO2.



Step 1: Calculate the volume of CO2 and air in the solution.

 Assume that we have 100 L of solution. The solute will be CO2.

%CO2(v/v) = vol of solutevol of solutionx 1004.6% = vol of CO2100 L solution×100VCO2 =  4.6 % CO2100×100 L solution 


VCO2 = 4.6 L CO2


Vair = 100 L - 4.6 L

Vair = 95.4 L air


Step 2: Calculate for the number of moles by using the Ideal Gas equation.

Since mass, temperature, and pressure are given, we will use the ideal gas equation to calculate for the moles.

PV = nRT

P = pressure, atm
 V = volume, L
 n = moles, mol
 R = gas constant = 0.08206 (L·atm)/(mol·K)
 T = temperature, K

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Problem Details

During a persons typical breathing cycle, the CO2 concentration in the expired air rises to a peak of 4.6% by volume.

Calculate the partial pressure of the CO2 in the expired air at its peak, assuming 1 atm pressure and a body temperature of 37oC .

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