in this question we are given pressure = 2.0 atm ( 202650 Pa) , volume = 30L and temperature = 27 °C. ( 300.15 K)
we are required to find the mols of the gas. we can do this using the ideal gas eaquation which is :
PV = nRT
where P - pressure
V - volume
n - mols
R - ideal gas constant
T - temperature.
when we rearange the equation to make n subject of the formula we get;
n = PV/RT
therefore the mols of the gas equal
n = ( 202650)(30)/ (8.3140)( 300.15)
= 0.2436236
= 0.244 mols (rounded off to thre decimals)