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I WISH I HAD SWEAT GLANDS. Equilibrium • Le. Chatelier’s Principle CO 2 + Ca. O Ca. CO 3 “chicken breath” “food” “egg shell” As temperature increases, chickens “pant” more. This stresses the system and shifts the equilibrium to the This makes the egg shells THIN and fragile. LEFT
I wish I had sweat glands. In a chicken… Ca. O + CO 2 In summer, [ CO 2 ] in a chicken’s blood -- shift Ca. CO 3 (eggshells) due to panting. ; eggshells are thinner How could we increase eggshell thickness in summer? [ CO 2 ] , shift -- give chickens carbonated water [ Ca. O ] , shift -- put Ca. O additives in chicken feed -- air condition the chicken house TOO much $$$ -- pump CO 2 gas into the chicken house would kill all the chickens!
Le. Chatelier’s Principle N 2 + 3 H 2 2 NH 3 + heat …favors the endothermic reaction (the reverse reaction) in which the rise in temperature is counteracted by the absorption of heat. Raising the temperature… Increasing the pressure… …favors the forward reaction in which 4 mol of gas molecules is converted to 2 mol. Decreasing the concentration of NH 3… Dorin, Demmin, Gabel, Chemistry The Study of Matter 3 rd Edition, page 532 …favors the forward reaction in order to replace the NH 3 that has been removed. Animation by Raymond Chang All rights reserved
Equilibrium Expression Haber Process N 2 + 3 H 2 Dorin, Demmin, Gabel, Chemistry The Study of Matter 3 rd Edition, page 532 2 NH 3 + heat
reversible reaction: Reactant Product Reactant and P R Product Acid dissociation is a reversible reaction. H 2 SO 4 equilibrium: 2 H 1+ + SO 42– Rate at which R P P R = looks like nothing is happening, however… system is dynamic, NOT static
Le Chatelier’s principle: When a system at equilibrium is disturbed, it shifts to a new equilibrium that counteracts the disturbance. N 2(g) + 3 H 2(g) Disturbance 2 NH 3(g) Equilibrium Shift Add more N 2…………………. . “ “ H 2…………………. . “ “ NH 3………………… Remove NH 3…………………. . Add a catalyst………………… Fritz Haber Increase pressure……………. no shift
Light-Darkening Eyeglasses Ag. Cl + energy (clear) Go outside… Ago + Clo (dark) Sunlight more intense than inside light; “energy” shift to a new equilibrium: GLASSES DARKEN Then go inside… “energy” shift to a new equilibrium: 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- --> Ag 0 + Cl 0 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+ + Cl 0 --> Cu 2+ + 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 Cu 2+ ions slowly move to the surface of the crystal where they interact with the silver metal: Cu 2+ + Ag 0 --> Cu+ + Ag+ The glass clears as the silver ions rejoin chloride ions in the crystals.