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At 25°C, gaseous SO2Cl2 decomposes to SO2(g) and Cl2(g) to the extent that 12.5% of the original SO2Cl2 (by moles) has decomposed to reach equilibrium. The total pressure (at equilibrium) is 0.900 atm. Calculate the value of Kp for this system.
Initially
mol SO2Cl2 = x
mol SO2 and mol Cl2 = 0
12.5%x mol SO2Cl2 decomposes to form 12.5%x mol SO2 and 12.5%x mol Cl2
At equilibrium
mol SO2Cl2 = x - 12.5%x = 87.5%x
mol Cl2 = 12.5%x
mol SO2 = 12.5%x
Kp = P(SO2) . P(Cl2) / P(SO2Cl2)
total mol gases at equil. = (87.5%x)+(12.5%x)+(12.5%x)=112.5%x
P(SO2) = 12.5%x / 112.5%x * 0.9 = 0.1
P(Cl2) = 12.5%x / 112.5%x * 0.9 = 0.1
P(SO2Cl2) = 87.5%x / 112.5%x * 0.9 = 0.864
Therefore Kp = 0.1^2 / 0.864 = 0.01157 atm