Answer
The first step is to use the ideal gas law equation: PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature.
Rearranging the equation to solve for n, we get:
n = PV/RT
Substituting the given values, we get:
n = (1.35 atm) x (11.2 L) / [(0.0821 atm·L/mol·K) x (298 K)]
n = 0.553 mol
Therefore, there are 0.553 moles of helium gas present in the 11.2L container at 298K and 1.35 atm.