Chemical Equilibrium

To understand chemical equilibrium you need to realise that

1. chemical reactions that are in equilibrium DO NOT go to completion. 
2. "reactants" and "products" are all present at equilibrium
3. the "things" that are in equilibrium are the "reactants" and "products" whose concentrations can be changed (that is, substances that exist in solution).
4. equilibrium is the state in which the rate of the forward reaction (reactants → products) is the same as the reverse reaction (products → reactants

Knowing this, we can then write:

• a mass-action expression (http://www.ausetute.com.au/massaction.html)

And then

• the equilibrium law expression (http://www.ausetute.com.au/equilibriumlaw.html)

Which at equilibrium, results in an expression for the

• equilibrium constant (http://www.ausetute.com.au/equicons.html)

Which can be used to:

• calculate concentration (http://www.ausetute.com.au/ricetable.html)
• determine the extent of a reaction (http://www.ausetute.com.au/kextent.html)
• determine the equilibrium constant for the reverse reaction (http://www.ausetute.com.au/kreverse.html)
• determine whether a chemical reaction is exothermic or endothermic (http://www.ausetute.com.au/ktemperature.html)