Question

Consider the reaction, NH4CO2NH2(s)<---. 2NH3(g)+CO2(g), which at 300K, the equilibrium constant, Kp is 0.030 atm3. When ammonium carbamate crystals, NH4CONH, are placed into a container with an unknown initial preassure of pure CO2, the crystals begin to decompose according to the reactio above. After equilibrium is reached, the ammonia pressure is found to be 0.200 atm.

a. Cacluate Kc for this reaction at 300K

b. calculate the total pressure in the container at equilibrium

c. calculate the pressure of pure CO2 originally in the contianer.

Answer 1

Kp = Kc(RT)^deln

deln= 2+1 =3

R =0.08206 L.atm/mole.K T =300 K

0.030 = Kc(0.08206*300)³

K_C= 0.030/14919.64 =2.01*10^-6

Pressure of ammonina at equilibium = 0.2 atm

KP = [PNH3]² [PCO2]

0.030= (0.2)³[PCO2]

[PCO2] =0.030/0.008 =3.75 atm

Total pressure at equilibrium = 3.75+0.2 = 3.95 atm

2 moles of NH3 forms along with 1 mole of CO2

0.2 atm of NH3 corresponds to 0.2/2 =0.1 atm of CO2

pressure of CO2 at equilibrium =0.1

Presure at equilibrium= 3.95= pressure of CO2 at equilibrium + pressure of CO2 at the begining + pressure of NH3 at equilibrium

pressure of CO2 at the begining= 3.95-0.1-0.2 =3.65 atm