Question

How many moles of O2 are in 53 L of O2 at STP?
A) 2.4
B) 0.45
C) 1.65
D) 1187

Answer 1

For Any gas:
P V = n R T
where:
P : pressure
V : volume
n : number of moles
R : gas constant
T : absolute temperature in kelvin
provided that:
V = 53 L
S.T.P means standard temperature and pressure at which pressure is 1 atm and temperature is 273 K 
R = 0.08205 atm.L /mol.K
So:
n = $\frac{P.V}{R.T}$ = $\frac{1atm * 53 L}{0.08205 * 273 K}$
= 2.4 moles
The correct answer is A) 2.4