The mass of of air at standard temperature and pressure is about

CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance

Problem

The mass of

1\,\mathrm{m^3}

of air at standard temperature and pressure is about

1.3\,\mathrm{kg}

, of which about

77\%

\mathrm{N_2}

and

23\%

\mathrm{O_2}

. (1) (a) (i) Calculate the mass of

\mathrm{N_2}

1\,\mathrm{m^3}

of air. (ii) If the molar mass of

\mathrm{N_2}

28\,\mathrm{g\,mol^{-1}}

, calculate the number of moles of

\mathrm{N_2}

1\,\mathrm{m^3}

of air. (iii) Hence, calculate the mass of an atom of nitrogen. (2) (b) (i) Calculate the mass of

\mathrm{O_2}

1\,\mathrm{m^3}

of air. (ii) If the molar mass of

\mathrm{O_2}

32\,\mathrm{g\,mol^{-1}}

, calculate the number of moles of

\mathrm{O_2}

1\,\mathrm{m^3}

of air. (iii) Hence, calculate the mass of an atom of oxygen.