Calculate the number of molecules of oxygen in one litre flask at `0^(@)C` and under a pressure of `10^(-12)` bar.

Explanation

Step I. No. of mass of `O_(2)`
`P = 10^(-12) "bar", V = 1 L, t = 0+273 = 273 K`.
According to ideal gas equation,
`PV = nRT , n = (PV)/(RT) = ((10^(-12) "bar") xx (1 L))/((0.083 L "bar" K^(-1) mol^(-1)) xx (273 K)) = 4.44 xx 10^(-14) mol`.
Step II. No of molecules of oxygen
No. of molecules `= "No. of moles" xx "Avogadro's no". = 4.44 xx 10^(-14) xx 6.022 xx 10^(23)`
`= 2.67 xx 10^(10)` molecules.