unit 4: systems at equilibrium

reversible reaction

a chem reaction that proceeds in the forward and reverse directions

chemical equilibrium

a state in a chemical system in which the forward and reverse reaction are occuring at the same rate

dynamic equilibrium

A chem system at equilibrium that is changing at the molecular level, but macroscopic properties are constant

characteristics of dynamic eq.

1. rate of fwd rxn = rate of rev rxn

2. Macroscopic properties (ex. color, pressure) are constant

3. The system is closed

equilibrum graph - fwd rxn (Ex: H₂ + I₂ → 2HI)

* Remember, chem equilibrium is where rate fwd rxn = rate bwd rxn, so the rate of reactants consumed equals the rate of products formed.

• H₂ and I₂ have a conc of 1, so they start at one and get consumed

• 2HI starts at 0, since none created, and more gets formed.

equilibrium graph - rev rxn (2HI —> H₂ + I₂

• 2HI starts at conc of 2, and gets consumed, while the prod start at zero and get formed.

equilibrium constant, K_eq

The ratio of equilibrium concentrations for a particular chemical system at a particular temperature

what is K_eq equal to

aA + bB ↔ cC + dD K = ([C]^c[D]^d)/