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.