In: Chemistry
A 0.831 gram sample of SO3 is placed in a 1.00 L rigid container and heated to 1100 K. The SO3 decomposes to SO2 and O2 :
2SO3(g) ↔ 2SO2(g) + O2(g)
At equilibrium, the total pressure in the container is 1.300 atm. Calculate the value of Kp at 1100 K
Extra Credit: Consider two containers A and B where A is a rigid container and B is a container with a massless, frictionless piston that maintains constant pressure. NH3(g) is injected into both containers and allowed to come to equilibrium. At equilibrium, 2 atm of Argon gas is injected into each container. Explain any changes (up, down or no change) to the equilibrium concentrations of NH3, N2and H2?
A 0.831 gram sample of SO3 is placed in a 1.00 L rigid container and heated to 1100 K. The SO3 decomposes to SO2 and O2 :
2SO3(g) ↔ 2SO2(g) + O2(g)
At equilibrium, the total pressure in the container is 1.300 atm. Calculate the value of Kp at 1100 K
Solution :- lets first calculate the moles of SO3
Moles of SO3 = 0.831 g / 80.0632 g per mol = 0.010379 mol SO3
Now lets calculate the initial pressure of the SO3
PV= nRT
P= nRT/V
= 0.010379 mol * 0.08206 L etm per mol K * 1100 K /1.0 L
= 0.9369 atm
2SO3 ----- > 2SO2 + O2
0.9369 atm 0 0
-2x +2x +x
0.9369-2x 2x x
At equilibrium total repssure is 1.30 atm
Value of x = 1.30 atm – 0.9369 atm
= 0.3631 atm
So the equilibrium pressures are as follows
SO3 = 0.9369 atm – 2x = 0.9369 atm – (2*0.3631 atm) = 0.211 atm
SO2 = 2x = 2*0.3631 atm = 0.7262 atm
O2 = 0.3631 atm
Now lets calculate the equilibrium constant
K = [SO2]^2[O2]/[SO3]^3
=[0.7262]^2[0.3631]/[0.211]^2
= 4.30
Extra Credit: Consider two containers A and B where A is a rigid container and B is a container with a massless, frictionless piston that maintains constant pressure. NH3 (g) is injected into both containers and allowed to come to equilibrium. At equilibrium, 2 atm of Argon gas is injected into each container. Explain any changes (up, down or no change) to the equilibrium concentrations of NH3 , N2 and H2 ?
Solution :- The container A which is rigid container when Ar is added to it then it increases the pressure in the container which causes the left shif in the equilibrium therefore the concentration of the NH3 will increase and concentration of the N2 and H2 will decrease.
The container with moving piston will reequilibrate and the concentrations of the NH3 and N2 and H2 will not change.