Question

In the average adult male, the residual volume (RV) of the lungs, the volume of air remaining after a forced exhalation, is 1,200. mL. (a) How many moles of air are present in the RV at 1.00 atm and 37.0°C? mol air (b) How many molecules of gas are present under these conditions?

Answer 1

Given,

Volume of air remaining after a forced exhalation = 1200 mL x( 1L /1000 mL) = 1.2 L

Pressure(P) = 1.00 atm

Temperature(T) = 37.0 ^oC + 273.15 = 310.15 K

a) We know,

The ideal gas equation,

PV = nRT

Rearranging the formula,

n = PV/RT

n = ( 1 atm x 1.2 L)/(0.08206 L.atm/mol.K x 310.15 K)

n = 0.0471 mol air

b) We know,

1 mol = 6.023 x 10²³ molecules

Now,

= 0.04715 mol air x (6.023 x 10²³ molecules / 1mol)

= 2.84 x 10²² molecules of gas are present under these conditions.