H 2(g) + I 2(g) 2HI (g) Write the K expression [H 2 ] = M [I 2 ] = M [HI] = 1.29 M

H 2(g) + I 2(g) 2HI (g) What is the equilibrium conc of [HI] if: [H 2 ] = 0.81 M [I 2 ] = M

Solve for K if: It is the reverse rxn The eqn is 1/3 of the original The eqn is reversed and is 4 times the original.

Equilibria with pressures? So far, we’ve only used concentration gases can be described in terms of pressures

PV = nRT P =(n/V]RT = CRT C= molar conc of gas K p is the equilibrium in terms of partial pressures of the gases

N 2(g) + 3H 2(g) 2NH 3(g) Write the K p expression How do K and K p relate? Let’s try it for this rxn… K= K p (RT) 2

H 2(g) + F 2(g) 2HF (g) Try it for this rxn… K = K p b/c sum of coefficients on either side is equal

General relationship K p = K(RT)  n n= the sum of the coefficients of the gaseous products minus the sum of the coefficients of the gaseous reactants

CH 3 OH (g) CO (g) + 2H 2(g) At 25 o C P CH3OH = 6.10 x atm P CO = atm P H2 = 1.34 atm What is K?

So far... Our systems have only involved gases! Homogeneous equilibria- where phases are all the same

Heterogeneous equilibria Equilibria involving more than one phase Take for instance… CaCO 3(s) CaO (s) + CO 2(g) Write the K

However... Experiments show that the position of heterogeneous equilibrium does not depend on the amounts of pure solids or liquids present!!

Why?? Concentrations of pure solids and liquids can NOT change!! So… LEAVE THEM OUT of K!! Let’s try…

Homework P 640 (WOW!) 22, 25, 28, 29, 31

To do now… Learn how to use “assignments” folder set groups for presentations set up chem olympics teams start homework!