Collisions of molecules against a wall

Exercise 1

Find the number of collisions against a wall of $1\;cm^2$ of a container containing oxygen at $1\;atm $ and $27^oC$.

$Z= \frac{P}{\sqrt{2\pi \cdot m\cdot k\cdot T}}=$ $\frac{1,033\cdot 10^5}{\sqrt{2\cdot 3,14 \cdot \frac{0,032}{6\cdot 10^{23}}\cdot 1,38\cdot 10^{-23}\cdot 300}}$ On $1cm^2$: $10^{-4}\frac{1,033\cdot 10^5}{\sqrt{2\cdot 3,14 \cdot \frac{0,032}{6\cdot 10^{23}}\cdot 1,38\cdot 10^{-23}\cdot 300}}=$ $1,13\cdot 10^{23}$ collisions