Equilibrium

• LeChatelier’s Principle

CO2 + CaO CaCO3

“chicken breath”

“food” “egg shell”

I WISH I HADSWEAT GLANDS.

As temperature increases, chickens “pant” more.This stresses the system and shifts the equilibrium to the LEFT

This makes the egg shells THIN and fragile.

[ CaO ] , shift

[ CO2 ] , shift

-- shift ; eggshells are thinner

In a chicken… CaO + CO2

CaCO3

(eggshells)

In summer, [ CO2 ] in a chicken’s blood due to panting.

How could we increase eggshell thickness in summer?

-- give chickens carbonated water

-- put CaO additives in chicken feed

-- air condition the chicken house TOO much $$$

-- pump CO2 gas into the chicken house

would kill all the chickens!

I wish I had sweat glands.

LeChatelier’s PrincipleN2 + 3 H2 2 NH3 + heat

Raising the temperature……favors the endothermic reaction (the reverse reaction) in which the rise in temperature is counteracted by the absorption of heat.

Increasing the pressure……favors the forward reaction in which 4 mol of gas molecules is converted to 2 mol.

Decreasing the concentrationof NH3…

…favors the forward reaction in order to replace the NH3 that has been removed.

Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 532 Animation by Raymond ChangAll rights reserved

Equilibrium Expression

322

23

eqHN

NHK

N2 + 3 H2 2 NH3 + heat

Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 532

Haber Process

reactants

productsKeq

reversible reaction:

H2SO4 2 H1+ + SO42–

Acid dissociation is a reversible reaction.

Rate at whichR P

Rate at whichP R=

looks like nothing is happening, however…system is dynamic, NOT static

equilibrium:

Reactant Product and P RReactant Product

Remove NH3…………………..

“ “ NH3…………………

“ “ H2…………………..

Add more N2…………………..

Le Chatelier’s principle

N2(g) + 3 H2(g) 2

NH3(g)

Le Chatelier’s principle:

Disturbance Equilibrium Shift

no shift

When a system at equilibrium is disturbed, it shifts to a new equilibrium that counteracts the disturbance.

Add a catalyst…………………

Increase pressure…………….Fritz Haber

shift to a new equilibrium:

Then go inside…

shift to a new equilibrium:

Light-Darkening Eyeglasses

AgCl + energy Ago + Clo

“energy”

Go outside… Sunlight more intense than inside light;

GLASSES DARKEN

(clear) (dark)

“energy”

GLASSES LIGHTEN

Sensitive Sunglasses Oxidation-reduction reactions are the basis for many interesting and useful applications of technology. One such application is photochromic glass, which is used for the lenses in light sensitive glasses. Lenses manufactured by the Corning Glass Company can change from transmitting 85% of light to only transmitting 22% of light when exposed to bright sunlight. Photochromic glass is composed of linked tetrahedrons of silicon and oxygen atoms jumbled together in a disorderly array, with crystals of silver chloride caught in between the silica tetrahedrons. When the glass is clear, the visible light passes right through the molecules. The glass absorbs ultraviolet light, however, and this energy triggers an oxidation-reduction reaction between Ag+ and Cl-:

Ag+ + Cl- --> Ag0 + Cl0

To prevent the reaction from reversing itself immediately, a few ions of Cu+ are incorporated into the silver chloride crystal. These Cu+ ions react with the newly formed chlorine atoms:

Cu+ + Cl0 --> Cu2+ + Cl-

The silver atoms move to the surface of the crystal and form small colloidal clusters of silver metal. This metallic silver absorbs visible light, making the lens appear dark (colored).

As the glass s removed from the light, the Cu2+ ions slowly move to the surface of the crystal where they interact with the silver metal:

Cu2+ + Ag0 --> Cu+ + Ag+

The glass clears as the silver ions rejoin chloride ions in the crystals.