chemistry ( le chant princ) and equilbrium

what is chemical equilibrium

The point when the forward and reverse reactions occur at equal rates.

-the forward and reverse reactions are still happening.

-their rates are equal

-the observable properties remain constant. this is called dynamic equilibrium, the reaction does not stop.

conditions required for equilibrium

-Macroscopic properties are constant. Ex. no observable change.

-Forward and reverse rates are equal. Ex. Both reactions happen at the same rate.

-A closed system is required. Ex. substances cannot escape.

-Equilibrium can be reached from either direction. Ex. you can start with reacants or products.

The 3 types of equilibrium: phase equilibrium

A substance change between physical states. Ex. liquid water and water vapor.

The 3 types of equilibrium: Solubility equilibrium

Dissolving and recrystallization occur at equal rates in a saturated solution. Ex. soild NaCl dissolving in water.

The 3 types of equilibrium: chemical equilibrium

A reversible chemical reaction occurs at equal forward and reverse rates.

Catalyst and surface area

A catalyst increases both reaction rates equally.

-It helps the system reach equilibrium faster.

-It does not shift the equilibrium

-Surface area has the same equilibrium effect as a catalyst.

endothermic

energy absorbed. Delta H pos

Exothermic

Energy released. Delta H neg.

Interpreting Kc.

Much greater than 1=products are favored

Much smaller than 1=reacants are favored

around 1= neither side is strongly favored

Ex. 1000=products are favored

0.001=reacants are favored