what is the difference between Qc and Kc and how it will calculate both?

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Sumeet Malik answered this

Reaction quotient is used to determine relative amounts of reactants and products at a particular point of time in the reaction where as equilibrium describes the same thing at equilibrium. Thus, the value of Q and k is s

For the reaction,

aA + bB ↔ cC + dD

Q_c defined as

Q_c= [D]^d[C]^c

[A]^a[B]^b

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Saurabh Ranjan answered this

Kc is equilibrium constant , it is used for predicting the extent of a reaction.

Qc is reaction quotient, is is used for predicting the direction of a reaction.

Saurabh Ranjan answered this

If Q_C > K_C, then the reaction will proceed in the reverse direction.
If Q_C< K_C, then the reaction will proceed in the forward direction.
If Q_C = K_C , then the reaction is at equilibrium.

Saurabh Ranjan answered this

For a general reaction,

Saurabh Ranjan answered this

Mathematically the same equation (1) is used for calculation Kc also. If we apply equation (1) to the reaction when it is already in equilibrium, it will give Kc but if we apply the same equation (1) at the time when reaction is not in equilibrium stage it will give the value of Qc. At equilibrium Qc becomes Kc.

Md Junaid answered this

Reaction Quotient Q_c- It is the function of the activities or concentrations of the species involved in a chemical reaction.

For a general reaction,

Thus it is the ratio of product of concentrations of the products and product of concentrations reactants, each concentration raised to the power equal to stoichiometric coefficient in the balanced equation at any stage of reaction.

Equilibrium constant K_c- The ratio of product of concentrations of the products and product of concentration reactants, each concentration raised to the power equal to stoichiometric coefficient in the balanced equation at only equilibrium stage of reaction.

Reaction Quotient Q_cpridicts the direction of reaction.

When Q_c< K_c: Reaction proceeds in forward direction

Q_{c >}K_c: Reaction proceeds in backward direction

Q_c= K_c: Reaction is in equilibrium

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Md Junaid answered this

K_c is ratio of rate constant of forward and backward reaction at equilibrium while Q_c is the ratio of rate constant of forward and backward reaction before coming to equilibrium or after equilibrium. Q_c becomes equal to K_c when rate of forward and backward reaction becomes equal.

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