A United Nations toxicologist studying the properties of mustard gas, S(CH2CH2Cl)2, a blistering agent used in warfare, prepares a mixture of 0.675 M SCl2 and 0.973 M C2H4 and allows it to react at room temperature (20.0°C ).
SCl2 (g) + 2 C2H4 (g) --> S(CH2CH2Cl)2 (g)
At equilibrium, [S(CH2CH2Cl)2] = 0.350 M. Calculate Kp.
I have worked this problem out a few times and what I have done so far is use an ice table. Found x = 0.350 M. Used the equation Kp = (C)/(A)(B). Can someone please help me figure out what I need to do right!
Why not show your work for the ICE table and let us see what you need to do. Otherwise we're just guessing what you've done.
It appears that you need Kc = (C)/(A)(B)^2 (Note: you don't have the squared term)
Then you have x, and I assume the rest of ICE table. If you did it right, A will be 0.675-x and B will be 0.973-2x and you have x. Plug those into Kc expression and solve, then Kp=Kc(RT)^delta n where delta n is 1-3 = -2.
To calculate the equilibrium constant Kp, we need to set up and solve the expression for Kp using the concentrations of the reactants and products at equilibrium.
The balanced equation for the reaction is: SCl2 (g) + 2 C2H4 (g) → S(CH2CH2Cl)2 (g)
Let's denote the initial concentrations of SCl2 and C2H4 as [SCl2] = 0.675 M and [C2H4] = 0.973 M, respectively.
Given that the equilibrium concentration of S(CH2CH2Cl)2 is [S(CH2CH2Cl)2] = 0.350 M, we can use this information to set up the following expression for Kp:
Kp = ([S(CH2CH2Cl)2]) / ([SCl2]^1) * ([C2H4]^2)
Plugging in the given values, Kp = (0.350) / (0.675)^1 * (0.973)^2
We can now calculate Kp:
Kp = (0.350) / (0.675) * (0.947)^2
Kp ≈ 0.460
Therefore, the equilibrium constant Kp for the reaction is approximately 0.460.
To find the value of Kp, you need to set up the equilibrium expression for the given reaction:
Kp = ([S(CH2CH2Cl)2]/P0)^x ([SCl2]/P0)^y ([C2H4]/P0)^z
Where x, y, and z are the stoichiometric coefficients of the balanced equation and P0 is the standard pressure, which is usually taken as 1 atm.
Given the balanced equation:
SCl2 (g) + 2 C2H4 (g) --> S(CH2CH2Cl)2 (g)
We can see that x = 1, y = 2, and z = -1. Note that the stoichiometric coefficient of C2H4 is multiplied by 2 because two moles of C2H4 are required to react with one mole of SCl2.
You have correctly obtained the equilibrium concentration of S(CH2CH2Cl)2 as 0.350 M. However, your approach to find Kp using the equation Kp = (C)/(A)(B) is incorrect. The equation you mentioned calculates the reaction quotient, not the equilibrium constant Kp.
To find Kp, you need to use the equilibrium expression and the concentrations at equilibrium:
Kp = ([S(CH2CH2Cl)2]/P0)^x ([SCl2]/P0)^y ([C2H4]/P0)^z
= (0.350/P0)([SCl2]/P0)^2 ([C2H4]/P0)^(-1)
Now, you need to substitute the equilibrium concentrations into the expression. The initial concentrations of SCl2 and C2H4 are given as 0.675 M and 0.973 M, respectively. However, you won't have enough information to solve for Kp without knowing the partial pressure of a reaction component because the Kp expression involves pressure.
If you have information about the partial pressures of any of the reactants or the product at equilibrium, you can use those values to calculate Kp. Otherwise, you would need additional information to determine the partial pressures at equilibrium in order to find the value of Kp.