What is "equal" in a chemical equilibrium?

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Answer 1 · 2016-12-08T19:08:13

The rate of the forward reaction as compared to the rate of the reverse reaction.

For the generalized equilibrium we have:

#A+BrightleftharpoonsC+D#

Now we have a rate forward,

#k_f[A][B]#, and a rate backwards, #k_r[C][D]#.

The condition of chemical equilibrium is reached when,

#"rate forward "-=" rate backwards"#,

i.e. #([C][D])/([A][B])=k_f/k_r=K_"eq"#.

#K_"eq"# is the thermodynamic equilibrium constant, WHICH must be measured for a given reaction, and for a given temperature.