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CHEMICAL EQUILIBRIUM Chapter 16. OBJECTIVE. Distinguish between reversible and completion reactions Understand Equilibrium Define/ apply the terms system and stress to reversible reactions Le Chatlier’s Principle. Reversible Reactions. H 2 + I 2 ↔ 2HI
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OBJECTIVE • Distinguish between reversible and completion reactions • Understand Equilibrium • Define/ apply the terms system and stress to reversible reactions • Le Chatlier’s Principle
Reversible Reactions H2 + I2 ↔ 2HI • the products may react back to original reactants. • “closed system”: ONLY if all reactant are present • If one piece is completely gone it has ”gone to competition” and no longer reversible
TWO REACTIONS • only difference is the Direction H2 + I2↔ 2HI reactants products 2HI ↔ H2 + I2 Left Right
Examples: Reversible Reactions. • Unopened Soda • Breathing • Rechargeable batteries • Color changing shirt
Equilibrium • The state in which a chemical reaction and its reverse reaction occur at the same rate.
Equilibrium achieved Reversible Reactions Product conc. increases and then becomes constant at equilibrium Reactant conc. declines and then becomes constant at equilibrium
“System” • Any reversible reaction H2 + I2↔ 2HI noted by the double arrow; ↔
“stressing a system” • Pick reversible reactions that have different colored products. • EXAMPLES T –shirt ball • Stress: done to change the ratio color change means change ratio of two products
Le Chatelier’s Principle • If a system at equilibrium is stressed, it will react to undo the stress.
Le Chatelier’s Principle • Anything YOUdo(stress) to a reversible reaction, the systemreacts in a way to UNDO that change • Remember there are TWO reactions going in every reversible reaction.
Shifting Equilibrium • Change Temperature • Change concentration of Cl- CuCl4(aq)↔ Cu+(aq)+ Cl-(aq)+ heat Left: GREEN Right BLUE • Add Temperature or Cl- : Green/ right • Remove heat or Cl: Blue / Left
Temperature ADD energy or REMOVE energy Will cause opposite results Science is fun 29778 bleaching
Concentration:Amount ADD reactant or REMOVE reactant Will cause opposite results Science is fun 31918 Cu and hydrogen
Pressure Used for gases Easiest way to measure the amount of a gas Same affect as changing the concentration
Equilibrium Disk 6C32 Pink to blue Co(H2O)6Cl2---> Co(H2O)4Cl2 + 2 H2O Equilibrium systems are • DYNAMIC (in constant motion) • REVERSIBLE • can be approached from either direction Blue to pink Co(H2O)4Cl2+ 2 H2O ---> Co(H2O)6Cl2
Le Chatelier’s Principle • If youADDreactants , The system will REMOVEreactants by making more products. • If youREMOVEreactants , The system will ADDreactants by USING (reacting) products.
LEFT: RIGHT: ↔
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STRESS to SYSTEM Three stress’s are • Temperature • Concentration • Pressure.