Question

Dalton's Law Of Partial Pressure show all calculations!!

a.) Earth's atmosphere consist of 78% N2 and 20% O2, and other gases. What is the partial pressure of N2 and O2 in torr, when atmospheric pressure is 1 atm?

b.) Ammonia is completely decomposed to nitrogen and hydrogen as in question 9b) At the end of the experiement the pressure of the gas mixture is 866 mmHg. Calculate the partial pressures of N2 and H2

Answer 1

(a)

mole fraction of N2 = 0.78

mole fraction of O2 = 0.2

atmospheric pressure = 1 atm

partial pressure of N2 = mole fraction x total pressure

                                    = 0.78 x 1

                                   = 0.78 atm             ( 1 atm = 760 torr)

                                  = 0.78 x 760

                                 = 592.8 torr

partial pressure of O2 = mole fraction x total pressure

                                   = 0.20 x 1

                                  = 0.20 atm

                                  = 0.20 x 760 torr

                                 = 152 torr

b)

2NH3 -------------------------> N2 + 3H2

total pressure = 866 mmHg

N2 moles = 1

H2 moles = 3

total moles = 4

mole fraction of N2 = 1/4 = 0.25

mole fraction of H2 = 3/4 =0.75

partial pressure of N2 = mole fraction x total pressure

                                   = 0.25 x 866

                                  = 216.5 mmHg

partial pressure of H2 = 0.75 x 866

                                   = 649.5 mmHg