-Keq is the ratio of products to reactants when the reaction is in equilibrium (k1 = k-1)

-wth each concentration raised to their respective coefficents

long, complicated form of Keq:

-where Пj denotes the product across all j-indexed variables, cj is the activity of species j, and νij is the stoichiometric number (the stoichiometric coefficient multiplied by +1 for products and –1 for starting materials).

more useful form of Keq:

Derivation:

-Q is the ratio of products to reactants at any given time

long, complicated version:

-where Пj denotes the product across all j-indexed variables, aj(t) is the activity of species j at time t, and νj is the stoichiometric number (the stoichiometric coefficient multiplied by +1 for products and –1 for starting materials)

useful version:

-NOTE: solid and liquid species are NOT included in Keq or Q (because solids and liquids are available in macroscopic amounts and react almost instantly; whereas aqueous ions and gases are sparse and have to diffuse through the solution to react)

-the reaction will move from Q to Keq

-when Q< Keq, the reaction will procede forward

-when Q>Keq, the reaction will procede backwards

-trick: imagine a number line

Keq vs Q Awesome Trick to Determine which direction a Reaction will go! Chemistry