How many moles of gas are in a volume of 48.6 L at STP?

1 Answer
Jun 26, 2016

2.17 moles of gas.


We are at STP, so we have to use the ideal gas law equation.
#PxxV = nxxRxxT#.

  • P represents pressure (could have units of atm, depending on the units of the universal gas constant)
  • V represents volume (must have units of liters)
  • n represents the number of moles
  • R is the universal gas constant (has units of #(Lxxatm)/ (molxxK)#)
  • T represents the temperature, which must be in Kelvins.

Next, list your known and unknown variables. Our only unknown is the number of moles. Our known variables are P,V,R, and T.

At STP, the temperature is 273K and the pressure is 1 atm. The proportionality constant, R, is equal to 0.0821 #(Lxxatm)/ (molxxK)#

Now we have to rearrange the equation to solve for n:

# n = (PV)/(RT)#

#n = (1cancel"atm"xx48.6cancelL)/(0.0821(cancel"Lxxatm")/(molxxcancel"K")xx273cancel"K"#
#n = 2.17 mol#