What is the Keq equation?

1 Answer
Feb 5, 2017

Answer:

For the reaction, #A+BrightleftharpoonsC+D# #;K_"eq"=([C][D])/([A][B])#.

Explanation:

#K_(eq)=([C][D])/([A][B])#

Given #A+BrightleftharpoonsC+D#, there is a #"rate forward"#, #k_f[A][B]#, and a #"rate backwards"#, #k_r[C][D]#; #k_f# and #k_r# are some unspecified rate constants.

Equilibrium, by definition, explicitly specifies EQUALITY of FORWARD and REVERSE rates, and thus:

#k_f[A][B]=k_r[C][D]#;

Under these conditions, chemical change has not ceased, but there is no net macroscopic change in the given concentrations.

Further we can write, #k_f/k_r=([C][D])/([A][B])#, and this is usually specified under standard conditions.

The quotient #k_f/k_r# is better as known #K_"eq"#, the thermodynamic equilibrium constant, and it must be measured for a given reaction.