An equilibrium mixture of PCl5(g), PCl3(g), and Cl2(g) has a partial pressure of 217.0 torr, 13.2 torr, and 13.2 torr, respectively. A quantity of Cl2(g) is injected into the mixture, and the total pressure jumps to 263.0 torr. The appropriate chemical equation is PCl3(g) + Cl2(g) <=> PCl5(g)
Calculate the new partial pressures of PCl3, Cl2, and PCl5
Am i supposed to find Kp first..? please help me!
Yes, I would find Kp first.
Hi lol
Is this correct?:
Kp = PPCl5/(PPCl3)(PCl2) = 217.0 torr/(13.2 torr)(13.2 torr) = 1.245
x/(263 torr - x) = 1.245
x = 327.435 - 1.245x
2.245x = 327.435
x = 145.85 torr = PPCl5
263.0 total torr - 145.85 PCl5 torr = 117.15 torr - 13.2 torr = 103.95 torr for Cl2
13.2 torr for Cl3?
I would do this. First I would convert torr to atm.
PPCl5 = 217/760 = 0.2855 atm
PPCl3 = 13.2/760 = 0.01737 atm.
PCl2 = 13.2/760 = 0.01737 atm
Total P = 243.4/760 = 0.3203 atm
Cl2 added = 263-243 = 19.6 and 19.6/760 = 0.02579
............PCl3 + Cl2 ==> PCl5
initial..0.01737.0.01737..0.2855
add.............0.02579..........
change.......-p....-p.......+2p
equil.0.01737-p.0.04316-p..0.2855+2p
Substitute into Kp expression with these ICE chart values and solve for p.
Hi Dr. Bob. I'm coming up with outrageous numbers for when I try to use atm's with my Kp value.. please look!
Kp = PPCl5/PPCl3PCl2 = (0.2855)/(0.01737)(0.01737) = 946.3
PCl3 : 0.01737-946.3 = -946.28 atm?!
Cl2 : 0.04316 - 946.3 = -946.26 atm o.o
PCl5 : 0.2855 + 2(946.3) = 1,892.8855 >.<
when i tried it with torr it gave me 11.955, 31.555, and 219.49 >.< am i reading your directions correctly?
ohh i'm sorry i understand now thank you Dr. Bob!
Yes, in order to find the new partial pressures of PCl3, Cl2, and PCl5, you will need to find the new equilibrium concentrations of each species using the given information and the equilibrium constant (Kp) for the reaction.
To find Kp, you need to set up the equilibrium expression using the balanced chemical equation:
PCl3(g) + Cl2(g) <=> PCl5(g)
The expression for Kp would be:
Kp = (PCl5)^a / (PCl3)^b * (Cl2)^c
In this case, the stoichiometric coefficients (a, b, c) for the balanced equation are 1, 1, and 1.
Now, you need to use the given partial pressures and the ideal gas law to calculate the initial concentrations of PCl3, Cl2, and PCl5. The ideal gas law is expressed as:
PV = nRT
Rearranging the equation, you get:
n = PV / RT
n is the number of moles, P is the pressure, V is the volume, R is the ideal gas constant (0.0821 L·atm/mol·K), and T is the temperature in Kelvin.
Using the initial partial pressures and the total pressure, you can calculate the initial and final number of moles of each species. Remember, the total pressure is the sum of the partial pressures of each gas in the mixture.
Once you have the initial and final number of moles, you can calculate the initial and final concentrations (molarities) of PCl3, Cl2, and PCl5.
Finally, you can use the equilibrium expression and the calculated concentrations to solve for Kp.
Once you have found Kp, you can use it and the new total pressure to calculate the new partial pressures of PCl3, Cl2, and PCl5 using the equilibrium expression.
I hope this explanation helps you solve the problem. If you have any further questions, feel free to ask!