J.R. S. answered 08/29/20
Ph.D. University Professor with 10+ years Tutoring Experience
Let's assume that temperature is 290 K (Kelvin.) If not, you add 273 to Celsius to get K.
Let's also assume that P is 1.5 atmospheres and V is 13 Liters.
The units for R is L-atm/K-mol
Thus, when you solve for n you have n = PV/RT = (1.5 atm)(13 L)/(0.082 L-atm/K-mol)(290K) = moles