Oxygen is present in a `1 L` flask at a pressure of `7.6xx10^(-10)mm Hg`. Calculate the number of oxygen molecules in the flask at `0^(@)C`.

Explanation

`n = (PV)/(RT)`....(i)
`P = (7.6 xx 10^(-10))/(760) = 10^(-12) atm`
`V = 1L, T = 273 K, R = 0.0821 L atm K^(-1) mol^(-1)`
From eq. (i) `n = (10^(12) xx 1)/(0.0821 xx 273)`
Number of molecules `= n xx 6.023 xx 10^(23)`
`= (10^(012))/(0.0821 xx 273) xx 6.023 xx 10^(23)`
`= 2.68 xx 10^(10)`