Ammonium carbamate NH2COONH4 is a salt of carbamic acid that

Ammonium carbamate (NH2COONH4) is a salt of carbamic acid that is found in the blood and urine of mammals. At 250.°C, Kc = 1.58 × 10^8 for the following equilibrium:

NH2COONH4(s) 2 NH3(g) + CO2(g)

If 10.80 g of NH2COONH4 is put into a 0.500L evacuated container, what is the total pressure at equilibrium?

Solution

           NH2COONH4(s) <===> 2 NH3(g) + CO2(g)

Dn = 3-0 = 3

kp = Kc*(RT)^Dn

   = (1.58*10^-8)*(0.0821*523.15)^3

   = 1.25*10^-3

Kp = pNH3^2*pCO2

( 1.25*10^-3) = (2x)^2*x

x = 0.068

pNH3 = 2x = 2*0.068 = 0.136 atm

pO2 = x = 0.068 atm

total pressure = 0.136+0.068 = 0.204 atm