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Master_Key:
Kp = (p[Cl2] * p[PCl3]) / p[PCl5]

Arthur Bon Zavi:

--- Quote from: Uchia on November 04, 2010, 08:01:34 am ---when some phosphorus penta chloride was heated to a temperature T in a container 78% OF IT decomposed and the pressure in the container was 2.2


PCl5(g)  backward  and forward reaction      PCL3(g) + CL2 (g)


could you please help me to solve this question and thanks

--- End quote ---

PCl5 <--------------> PCl3(g)  +  Cl2(g)

1 mole of phosphorous-penta-chloride was heated, i.e 100 %, 78 % decomposed ! i.e 78 % of 1 mole..

Therefore : 78 / 100 = 0.78 moles

                              [PCl3] X [Cl2]
 Kp =      ----------------------------------------
                                    [PCl5]

Total : 0.78 + 0.78 + 0.78 = 2.34

Fraction of PCl5 =  0.78        1
                            ------- =  --- (Same is for PCl3 and Cl2).
                             2.34        3

2.2 MPa X 1000 = 2200 KPa

(1/3) (2200) = 733.3 ----------------------> Partial pressure for the three.

Therefore Kp = (733.3)2 / 733.3 = 733.3 KPa

Is this the answer ?

Uchia:
mm no

anyways thnxs for your help I found the answer

Initial          PCl5                           PCl3           Cl2
                    1                                0               0
Change
                 1-0.78=0.22                0.78        0.78     

Total mole 0.22 + 0.78 + 0.78 = 1.78

(0.22/1.78) * 2.2
(0.78/1.78) * 2.2
(0.78/1.78) * 2.2

then continue

see the problem was that       for PCl5 you take the amount left the one that was unreacted this is done by subtraction because at equilibrium you should use the amount of both the reactants and the products in the experimen and using the amount that decomposed could not be used because it already changed to products

Arthur Bon Zavi:

--- Quote from: Uchia on November 04, 2010, 10:00:03 am ---mm no

anyways thnxs for your help I found the answer

Initial          PCl5                           PCl3           Cl2
                    1                                0               0
Change
                 1-0.78=0.22                0.78        0.78     

Total mole 0.22 + 0.78 + 0.78 = 1.78

(0.22/1.78) * 2.2
(0.78/1.78) * 2.2
(0.78/1.78) * 2.2

then continue

see the problem was that       for PCl5 you take the amount left the one that was unreacted this is done by subtraction because at equilibrium you should use the amount of both the reactants and the products in the experimen and using the amount that decomposed could not be used because it already changed to products

--- End quote ---

Oh! Yeah. Sorry. Just near. :(

But was that 2.2 MPa Or KPa ?

Uchia:
kpa maybe

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