How many moles of oxygen are present in a 550 cm^3 sample of a gas at a pressure of 1.5 atm and at a temperature of 27^@C? (Given, R = 8.31 kPa dm^3 K^(-1) mol^(-1)).

How many moles of oxygen are present in a 550 cm^3 sample of a gas at

1.	How many moles of oxygen are present in a 550 cm^3 sample of a gas at a pressure of 1.5 atm and at a temperature of 27^@C? (Given, R = 8.31 kPa dm^3 K^(-1) mol^(-1)).
Answer» Solution :Since the value of R is given in k Pa `dm^3 K^(-1) mol^(-1)` (SI unit), the units of pressure and volume must correspond to it i.e., pressure should be EXPRESSED in k Pa and volume in `dm^3`. Therefore, `P= 1.5 atm = 1.5 xx 101.325 = 152 k Pa "" ( :. 1 atm = 101.325 k Pa)` `V = 550 cm^3 = 550 xx 10^(-3) dm^3 = 0.550 dm^3 ( :. 1 cm^3 = 10^(-3) dm^3)` `T = 27^@C = 273 + 27 = 300 K " and " N` = ? ACCORDING to the ideal gas equation, PV = nRT or `n= (PV)/(RT)=( 152 xx 0.550)/( 8.31 xx 300) =3.35xx10^(-2)` moles.