CHEMICAL EQUILIBRIUM

1. CHEMICAL EQUILIBRIUM 4/11/16 LeChatelier FILE 997

2. REVIEW OF CHEMICAL EQUILIBRIUM • CHEMICAL EQUILIBRIUM IS ESTABLISHED WHEN THE FORWARD RATE EQUALS THE REVERSE RATE. • A + B C + D • THE FORWARD REACTION PRODUCES PRODUCT (C, D) AND CONSUMES REACTANT (A,B). • THE REVERSE REACTION PRODUCES (REGENERATES) REACTANT (A,B) AND CONSUMES PRODUCT (C,D). • THE REACTION BEGINS WITH ONLY REACTANTS. • WHEN EQUILIBRIUM IS REACHED BOTH PRODUCT ANDREACTANT REMAIN. • SOME EQUILIBRIA PRODUCE LITTLE PRODUCT, AND ARE SAID TO FAVOR THE LEFT (REACTANT SIDE). • SOME EQUILIBRIA PRODUCE SIGNIFICENT PRODUCT, AND THE EQUILIBRIUM FAVORS THE RIGHT (PRODUCT SIDE). • WHEN EQUILIBRIUM IS ESTABLISHED, THE QUANTITIES OF PRODUCTS AND REACTANTS ARE STABLE AND CONSTANT. MEASURED BY MOLARITY, MASS OR GAS PRESSURE. FORWARD RATE REVERSE RATE

3. Le Catelier’s Principle • WHEN A REVERSABLE REACTION ESTABLISHES • EQUILIBRIUM, IT WILL RESIST ANY EXTERNAL STRESS • TO MAINTAIN THAT EQUILIBRIUM POSITION AND THE • EQUILIBRIUM CONCENTRATIONS. • EXTERNAL STRESSES INCLUDE: • CHANGING THE CONCENTRATION OF A REACTANT OR • PRODUCT. • INCREASING OR DECREASING THE MOLARITY OF ANY • REACTANT OR PRODUCT. • CHANGING THE TEMPERATURE, • CHANGING THE PRESSURE APPLIED TO REACTIONS WITH • GASES.

4. Le Catelier’s Principle…CONCENTRATION • IF YOU ADD TO THE LEFT (REACTANT) SIDE, THE SYSTEM WILL: • TRY TO REMOVE OR CONSUME WHAT YOU ADDED. • INCREASE COLLISIONS BETWEEN THE REACTANTS WHICH SPEEDS UP THE • FORWARD RATE OVER THE REVERSE TEMPORARILY. • PRODUCE MORE PRODUCT AND CONSUME MORE REACTANT. • EXAMPLE ADDING (INCREASING MOLARITY OF ) A IN THE REACTION: • A + B C + D • THE FORWARD RATE IS INCREASED PREFFERENTIALLY. • PRODUCTS C AND D INCREASE. • AS C AND D INCREASE THE COLLISIONS BETWEEN THEM INCREASE. • THE REVERSE RATE INCREASES UNTIL THE RATES ARE EQUAL AND A NEW EQUILBRIUM IS ESTABLISHED FORWARD RATE • INCREASING A WILL CAUSE MORE COLLISIONS BETWEEN A AND B, • THE FORWARD RATE WILL INCREASE. • A WILL INCREASE THEN DECREASE AS IT IS REACTED. • B WILL DECREASE AS IT IS REACTED (CONSUMED)

5. Le Catelier’s Principle…CONCENTRATION • IF YOU ADD TO THE RIGHT (PRODUCT) SIDE, THE SYSTEM WILL: • TRY TO REMOVE OR CONSUME WHAT YOU ADDED. • INCREASE COLLISIONS BETWEEN THE PRODUCTS WHICH SPEEDS UP THE • REVERSE RATE OVER THE FORWARD TEMPORARILY. • PRODUCE MORE REACTANT AND CONSUME MORE PRODUCT. • EXAMPLE ADDING (INCREASING MOLARITY OF ) C IN THE REACTION: • A + B C + D REVERSE RATE • THE REVERSE RATE IS INCREASED PREFFERENTIALLY. • REACTANTS A AND B INCREASE. • AS A AND B INCREASE THE COLLISIONS BETWEEN THEM INCREASE. • THE FORWARD RATE INCREASES UNTILL THE RATES ARE EQUAL AND A NEW EQUILBRIUM IS ESTABLISHED • INCREASING C WILL CAUSE MORE COLLISIONS BETWEEN C AND D, • THE REVERSE RATE WILL INCREASE. • C WILL INCREASE THEN DECREASE AS IT IS REACTED. • D WILL DECREASE AS IT IS REACTED (CONSUMED)

6. Le Catelier’s Principle…CONCENTRATION • IF YOU REMOVE FROM THE RIGHT (PRODUCT) SIDE, THE SYSTEM WILL: • TRY TO REPLACE OR PRODUCE WHAT YOU REMOVED. • DECREASE COLLISIONS BETWEEN THE PRODUCTS WHICH SLOWS THE • REVERSE RATE COMPARED TO THE FORWARD TEMPORARILY. • PRODUCE MORE PRODUCT AND CONSUME MORE REACTANT. • EXAMPLE REMOVING (DECREASING MOLARITY OF ) C IN THE REACTION: • A + B C + D FORWARD RATE • THE REVERSE RATE IS DECREASED PREFFERENTIALLY. • REACTANTS A AND B DECREASE. • AS A AND B DECREASE THE COLLISIONS BETWEEN THEM DECREASE. • THE FORWARD RATE DECREASES UNTILL THE RATES ARE EQUAL AND A NEW EQUILBRIUM IS ESTABLISHED • DECREASING C WILL CAUSE LESS COLLISIONS BETWEEN C AND D, • THE REVERSE RATE WILL DECREASE, FORWARD IS NOW FASTER. • C WILL DECREASE THEN INCREASE.. • D WILL INCREASEAS IT IS PRODUCED.

7. Le Catelier’s Principle…CONCENTRATION • IF YOU REMOVE FROM THE LEFT (REACTANT) SIDE, THE SYSTEM WILL: • TRY TO REPLACE OR PRODUCE WHAT YOU REMOVED. • DECREASE COLLISIONS BETWEEN THE REACTANTS WHICH SLOWS THE • FORWARD RATE COMPARED TO THE REVERSE TEMPORARILY. • PRODUCE MORE REACTANT AND CONSUME MORE PRODUCT. • EXAMPLE REMOVING (DECREASING MOLARITY OF ) A IN THE REACTION: • A + B C + D REVERSE RATE • THE FORWARD RATE IS DECREASED PREFFERENTIALLY. • PRODUCTS C AND D DECREASE. • AS C AND D DECREASE THE COLLISIONS BETWEEN THEM DECREASE. • THE REVERSE RATE DECREASES UNTILL THE RATES ARE EQUAL AND A NEW EQUILBRIUM IS ESTABLISHED • DECREASING A WILL CAUSE LESS COLLISIONS BETWEEN A AND B, • THE FORWARD RATE WILL DECREASE, REVERSE IS NOW FASTER. • A WILL DECREASE THEN INCREASE.. • B WILL INCREASEAS IT IS PRODUCED.

8. Le Catelier’s Principle…PRESSURE • IF THE PRESSURE EXERTED ON AN EQUILIBRIUM REACTION IS INCREASED: • THE REACTION WILL SHIFT TO THE SIDE WITH THE LEAST MOLES OF GAS. • ACCORDING TO BOYLES LAW AS P INCREASES VOLUME DECREASES, THE VOLUME OF FEWER MOLES OF GAS IS LESS, SHIFT TO THE SIDE WITH FEWEST MOLES OF GAS. • EXAMPLE INCREASING THE PRESSURE ON THE FOLLOWING REACTION WILL: • A(g) + B(g) C(g) + D(s) FORWARD RATE • THERE ARE 2 TOTAL MOLESOF GAS ON THIS SIDE. • MORE GAS COLLISIONS PUSH THE REACTION TO THE OPPOSITE SIDE, FORWARD IN THIS REACTION. • THE VOLUME OF 2 GAS MOLES IS GREATER THAN ON, THERFORE THE REACTION GOES TO THE OTHER SIDE WHICH HAS ONLY ONE MOLE OF GAS • THE ONE MOLE OF GAS OCCUPIES LESS VOLUME, ACCORDING TO BOYLE THAT IS LOGICAL….SHIFT TO THIS SIDE.

9. Le Catelier’s Principle…PRESSURE • IF THE PRESSURE EXERTED ON AN EQUILIBRIUM REACTION IS DECREASED: • THE REACTION WILL SHIFT TO THE SIDE WITH THE MOST MOLES OF GAS. • ACCORDING TO BOYLES LAW AS DECREASES VOLUME INCRESES, THE VOLUME OF MOST MOLES OF GAS IS MORE, SHIFT TO THE SIDE WITH MOST MOLES OF GAS. • EXAMPLE INCREASING THE PRESSURE ON THE FOLLOWING REACTION WILL: • A(g) + B(g) C(g) + D(s) REVERSE RATE • THERE ARE 2 TOTAL MOLESOF GAS ON THIS SIDE. • THE VOLUME OF 2 GAS MOLES IS GREATER THAN ONE, THERFORE THE REACTION GOES TO THIS SIDE AS PRESSURE IS DECREASED, DECREASE PRESSURE INCREASE VOLUME. • THE ONE MOLE OF GAS OCCUPIES LESS VOLUME, ACCORDING TO BOYLE THAT IS LOGICAL….SHIFT TO THE OTHER SIDE WHERE MORE MOLES (2) HAVE GREATER VOLUME WHEN PRESSURE DECREASES.