1. How many moles of oxygen will occupy a volume of 2.5 liters at 1.2 atm and 25 °C?

PV = V (1.2 n. 0821) (298) = 123 mols 2.

Explanation:

We need to use the ideal gas law for this problem, which states that:

PV=nRT

P is pressure in atmospheric pressures (in this case)

V is volume in liters (in this case)

n is moles of the substance

R is the gas constant (for this case, we use 0.082l atm mol−1K−1)

T is the temperature in Kelvin (as always)

Plugging in the known values, V=2.5l, P=1.2atm, T=298K, we get

n=PVRT=1.2⋅2.5298⋅0.082≈0.122 moles

So, there will be 0.122 moles of oxygen gas.