A sample of CaSO4(s) is placed in a container and then heated so that it decomposes according to the following equation:
2 CaSO4(s) ==> 2 CaO(s) + 2 SO2(g) + 02(g) At equilibrium, the total pressure in the container was found to be 0.60 atm at 700 C. Calculate Kp-
The reaction is as:
- CaSO4(s) --> 2CaO(s) + 2SO2(g) + O2(g)
Total pressure = 0.60atm at 700oC.
Kp = ?
We know, equilibrium Kp is written via the formula
- Kp = Product of Partial pressure of products/ Product of Partial pressure of reactants = (pSO2(g))^2 x pO2(g)
- where pSO2(g) and pO2(g) are the partial pressures of the SO2 and O2 gas
Furthermore, at equilibrium; Total pressure is the sum of the partial pressures of SO2 and O2 gas.
- Total pressure, pTOTAL = pSO2(g) + pO2(g)
At equilibrium, the pressures of the gases become:
pSO2(g) = 2x
pO2(g) = x
Meaning, 2x + x = pTOTAL
2x + x = 0.60atm
3x = 0.60atm
x = 0.60atm/3 = 0.2atm
pSO2(g) = 2x = 2 x 0.2atm = 0.4atm
pO2(g) = x = 0.2atm
Thus, the value of Kp is as:
Kp = (pSO2(g) )^2 x pO2(g)
Kp = (0.4 atm)^2 x 0.2vatm = 0.032
Kp = 0.032