Question

For nitrogen the molar volume at s.t.p is 0.0024m³ and the relative molecular mass is 28. Calculate the number of molecules in one cm³ of nitrogen at s.t.p

Answer 1

$1cm^3 = 1 × 10^{-6}m^3\\ \begin{aligned} \\ 0.0224m^3 &= 1\ mole\\ 1×10^{-6} m^3&= x\ mole \end{aligned}$

$\begin{aligned} x&= \dfrac{1×10^{-6}}{0.0224} = 4.464×10^{-5}moles \end{aligned}$

$\begin{aligned} \textsf{number}&\textsf{ of molecules} = 4.464×10^{-5}moles × N_A\\ &=4.464×10^{-5}moles × 6.02× 10^{23} molecules\\ &= 2.69× 10^{19} molecules \end{aligned}$