How many moles of oxygen are present in `400 cm^(3)` sample of the gas at a pressure of `760 mm Hg` and a temperature of `27^(@)C`. (The value of `R` is given to be `8.31 kPa dm^(3) K^(-1) mol^(-1)`.

Explanation

Since the value of `R` is given in `SI units`, it is necessary to express the pressure and volume in `kPa` and `dm^(3)`, respectively.
Thus, `P=760mm=101.3 kPa`
`V=400 cm^(3)=400xx10^(-3) dm^(3)=0.4 dm^(3)`
`T=27^(@)C=27+273=300K`
According to the ideal gas equation `PV=nRT`,
`n=(PV)/(RT)=(101.3xx0.40)/(8.31xx300)=0.0162=1.62xx10^(-2)mol`