How many moles is 135 L of ammonia gas at STP?

1 Answer
Aug 19, 2016

Answer:

#6.02 "moles"#

Explanation:

Since we're at STP, we can 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:

#color(red)("Known variables:")#
#P#
#V#
#R#
#T#

#color(blue)("Unknown variables:")#
#n#

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)#

Plug in the given values:

#n = (1cancel"atm"xx135cancelL)/(0.0821(cancel"Lxxatm")/(molxxcancel"K")xx273cancel"K"#
#n = 6.02 mol#