1.5 mole of PCl5 are heated at constant temperature in a closed vessel of 4 litres capacity.At the equilibrium,PCl5 is 35percent dissociated into PCl3 and Cl2.calculate the equilibrium constant.
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To calculate the equilibrium constant (Kc) for the reaction, we need to use the expression for Kc and the given information about the balanced equation and the extent of dissociation.
The balanced chemical equation for the dissociation of PCl5 is:
PCl5 ⇌ PCl3 + Cl2
According to the given information, at equilibrium, PCl5 is 35% dissociated. This means that the concentration of PCl5 remaining at equilibrium is 65% (100% - 35%), and the concentrations of PCl3 and Cl2 formed are both 35%.
To calculate the equilibrium constant Kc, we first need to find the concentrations of the reactants and products at equilibrium. Since the total volume of the closed vessel is 4 liters, we can use the information to find the concentrations in terms of moles per liter.
1. Calculate the initial moles of PCl5:
Given moles of PCl5 = 1.5 moles
2. Calculate the initial concentration of PCl5:
Initial concentration of PCl5 = (moles of PCl5) / (volume of vessel)
= 1.5 moles / 4 liters
= 0.375 M
3. Since PCl5 is 35% dissociated at equilibrium, the concentration of PCl5 at equilibrium is:
Concentration of PCl5 at equilibrium = Initial concentration of PCl5 - (Initial concentration of PCl5 x percentage dissociation of PCl5)
= 0.375 M - (0.375 M x 0.35)
= 0.375 M - 0.13125 M
= 0.24375 M
4. Since PCl5 dissociates into PCl3 and Cl2 in a 1:1 molar ratio, the equilibrium concentrations of PCl3 and Cl2 are both equal to the concentration of PCl5 at equilibrium:
Concentration of PCl3 at equilibrium = 0.24375 M
Concentration of Cl2 at equilibrium = 0.24375 M
5. Finally, the equilibrium constant Kc is calculated using the concentrations of the reactants and products at equilibrium:
Kc = (concentration of PCl3) x (concentration of Cl2) / (concentration of PCl5)
= (0.24375 M) x (0.24375 M) / (0.24375 M)
= 0.24375
Therefore, the equilibrium constant (Kc) for the dissociation of PCl5 is 0.24375.
To calculate the equilibrium constant, we first need to write the balanced chemical equation for the dissociation of PCl5:
PCl5 ⇌ PCl3 + Cl2
The reaction can be represented in terms of moles:
1 mol PCl5 ⇌ 1 mol PCl3 + 1 mol Cl2
Given that 1.5 moles of PCl5 are present initially, and at equilibrium, only 35% of it is dissociated, we can calculate the equilibrium concentrations of PCl5, PCl3, and Cl2.
Initial concentration of PCl5 = 1.5 moles / 4 L (volume of the vessel) = 0.375 M
At equilibrium, PCl5 concentration = (1 - 0.35) * 0.375 M = 0.35 * 0.375 M = 0.13125 M
PCl3 and Cl2 are both produced in equal amounts during the dissociation, so their concentrations at equilibrium will be the same:
PCl3 concentration at equilibrium = Cl2 concentration at equilibrium = (0.35 * 0.375 M) / 2 = 0.065625 M
Now, we can calculate the equilibrium constant (Kc) using the equation:
Kc = ([PCl3] * [Cl2]) / [PCl5]
Kc = (0.065625 M * 0.065625 M) / 0.13125 M = 0.034412 M²
Therefore, the equilibrium constant for the dissociation of PCl5 is 0.034412 M².
(PCl5) = 1.5 mols/4 L = 0.375 M.
0.375 M x 0.35 = 0.131 M
.......PCl5 ==> PCl3 + Cl2
I....0.375.......0......0
C.....-x.........x......x
E...0.375-x......x......x
Kc = (PCl3)(Cl2)/(PCl5)
You know x is 0.131 M. Substitute and solve for Kc.
Post your work if you get stuck.