Slides Shown Friday Nov. 7, 2008

In this sweeping view, the 10 kilometer-wide crater Heimdall lies on the north polar plains of Mars. But the bright spot highlighted in the inset is the Phoenix lander parachuting toward the surface. The amazing picture was captured on May 25 2008 by the HiRISE camera onboard the Mars Reconnaissance Orbiter. Though the lander looks like it might be dropping straight into Heimdall, it is really descending about 20 kilometers in front of the crater, in the foreground of the scene. The orbiter was 760 kilometers away from Phoenix when picture was taken, at an altitude of 310 kilometers. APOD 5/30/2008

Nitrogen dioxide shown immediately after expanding

Reaction of 2NO2(g) and N2O4(g) over time in a closed vessel

Reddish brown nitrogen dioxide, NO2 (g)

Reaching Equilibrium on the Macroscopic and Molecular Level

N2O4 (g) 2 NO2 (g)

Colorless Brown

The State of Equilibrium

At equilibrium: rateAt equilibrium: ratefwdfwd = rate = raterevrev

ratefwd = kfwd[N2O4] raterev = krev[NO2]2

For the Nitrogen dioxide - dinitrogen tetroxide equilibrium:

N2O4 (g, colorless) = 2 NO2 (g, brown)

kfwd[N2O4] = krev[NO2]2 kfwd [NO2]2

krev [N2O4]= = Keq

1) Small k N2 (g) + O2 (g) 2 NO(g) K = 1 x 10 -30

2) Large k 2 CO(g) + O2 (g) 2 CO2 (g) K = 2.2 x 1022

3) Intermediate k 2 BrCl(g) Br2 (g) + Cl2 (g) K = 5

Reaction Direction and the Relative Sizes of Q and K

Initial and Equilibrium Concentrations for theN2O4-NO2 System at 100°C

Initial Equilibrium Ratio

[N2O4] [N2O4] [N2O4][NO2] [NO2] [NO2]2

0.1000 0.0000 0.0491 0.1018 0.211

0.0000 0.1000 0.0185 0.0627 0.212

0.0500 0.0500 0.0332 0.0837 0.211

0.0750 0.0250 0.0411 0.0930 0.210

Changes in concentration with time for the reaction

H2O(g) + CO(g) H2 (g) + CO2 (g)

H2O and CO are mixed in equal numbers

H2O(g) + CO(g) H2 (g) + CO2 (g)

Changes with time in the rates of forward and reverse reactions

H2O(g) + CO(g) = H2 (g) + CO2 (g)

Concentration profile for the reactionN2 + 3H2 = 2NH3