How many moles of o2 are in 53 l of o2 at stp? a) 2.4 b) 0.45 c) 1.65 d) 1187

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 =  = 
= 2.4 moles
The correct answer is A) 2.4

Rn in the right answer