Question

Calculate the number of molecules in a deep breath of air whose volume is 2.35 L at body temperature, 36 ∘C, and a pressure of 735 torr.

Express the answer in molecules to three significant figures.

The adult blue whale has a lung capacity of 5.0×103 L. Calculate the mass of air (assume an average molar mass 28.98 g/mol) contained in an adult blue whale’s lungs at 0.5 ∘C and 1.10 atm, assuming the air behaves ideally.

Express the answer in kilograms to two significant figures.

Answer 1

volume = 2.35 L

temperature = 36 + 273 = 309 K

pressure = P = 735 torr = 0.967 atm

P V = n R T

0.967 x 2.35 = n x 0.0821 x 309

n = 0.0896

number of molecules = 0.0896 x 6.023 x 10^23

                                  = 5.40 x 10^22

problem 2 :

P V = n R T

1.10 x 5 x 10^3 = n x 0.0821 x 273.5

n = 244.94

mass = 244.94 x 28.98

          = 7098.4 g

           = 7.1 kg