Sat October 22, 2011 By:

What is the relation between Qc and Kc ?? Reply soon..

Expert Reply
Sun October 23, 2011
The reaction quotient, Q, is the same as the equilibrium constant expression, 
but for partial pressures or concentrations of the reactants and products before the 
system reaches equilibrium.
For a reaction: 
SO2Cl2(g)  SO2(g) + Cl2(g)
Q may be expressed as the following equations:

Qc can be used to determine which direction a reaction will shift to reach equilibrium.  
If Kc > Qc, a reaction will proceed forward, converting reactants into products. 
If Kc < Qc, the reaction will proceed in the reverse direction, converting products into reactants.  If Q = K then the system is already at equilibrium. 

and if, Kc = Qc , equilibrium has been reached

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