Kp help please
his question relates to the equilibrium gas-phase synthesis of sulphur trioxide:
16
2SO2(g) + O2(g) 2SO3(g)
Thermodynamic data for the components of this equilibrium are:
Substance ΔH / kJ mol−1 S / J K-1 mol-1
SO3(g) −396 ΔS+257
SO2(g) –297 ΔS+248
O2(g) 0 ΔS+204
This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm3. At equilibrium, the vessel contains 0.0500 mol of SO2(g), 0.0800 mol of O2(g) and 0.0700 mol of SO3(g).
With pressures expressed in MPa units, the value of the equilibrium constant, Kp, is
A 4.90
B 6.48
C 9.07
D 16.8
i tried 0.0700/(0.0500+0.0800+0.0700)x540=0.0006481
and the mark scheme says C im confused
16
2SO2(g) + O2(g) 2SO3(g)
Thermodynamic data for the components of this equilibrium are:
Substance ΔH / kJ mol−1 S / J K-1 mol-1
SO3(g) −396 ΔS+257
SO2(g) –297 ΔS+248
O2(g) 0 ΔS+204
This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm3. At equilibrium, the vessel contains 0.0500 mol of SO2(g), 0.0800 mol of O2(g) and 0.0700 mol of SO3(g).
With pressures expressed in MPa units, the value of the equilibrium constant, Kp, is
A 4.90
B 6.48
C 9.07
D 16.8
i tried 0.0700/(0.0500+0.0800+0.0700)x540=0.0006481
and the mark scheme says C im confused
Original post by Hi freinds
his question relates to the equilibrium gas-phase synthesis of sulphur trioxide:
16
2SO2(g) + O2(g) 2SO3(g)
Thermodynamic data for the components of this equilibrium are:
Substance ΔH / kJ mol−1 S / J K-1 mol-1
SO3(g) −396 ΔS+257
SO2(g) –297 ΔS+248
O2(g) 0 ΔS+204
This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm3. At equilibrium, the vessel contains 0.0500 mol of SO2(g), 0.0800 mol of O2(g) and 0.0700 mol of SO3(g).
With pressures expressed in MPa units, the value of the equilibrium constant, Kp, is
A 4.90
B 6.48
C 9.07
D 16.8
i tried 0.0700/(0.0500+0.0800+0.0700)x540=0.0006481
and the mark scheme says C im confused
16
2SO2(g) + O2(g) 2SO3(g)
Thermodynamic data for the components of this equilibrium are:
Substance ΔH / kJ mol−1 S / J K-1 mol-1
SO3(g) −396 ΔS+257
SO2(g) –297 ΔS+248
O2(g) 0 ΔS+204
This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm3. At equilibrium, the vessel contains 0.0500 mol of SO2(g), 0.0800 mol of O2(g) and 0.0700 mol of SO3(g).
With pressures expressed in MPa units, the value of the equilibrium constant, Kp, is
A 4.90
B 6.48
C 9.07
D 16.8
i tried 0.0700/(0.0500+0.0800+0.0700)x540=0.0006481
and the mark scheme says C im confused
Kp = p(SO3)^2/ p(SO2)^2 x p(SO2)^2
You have tried to find p(SO3). (The value is wrong but the method is correct) Correct the value and now find the other partial pressures
p(SO2) = 135 kPa = 0.135 MPa
p(SO3) = 189 kPa = 0.189 MPa
p(O2) = 216 kPa = 0.216 MPa
so Kp = 0.189^2/ [0.135^2 x 0.216 ] giving 9.07 hence C
Check your calculation
https://www.wolframalpha.com/input/?i=0.0700%2F(0.0500%2B0.0800%2B0.0700)*540
Use a calculator; don't do it by hand
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