Transcript 997LECHATELIER

CHEMICAL EQUILIBRIUM
4/11/16 LeChatelier FILE 997
REVIEW OF CHEMICAL EQUILIBRIUM
1) CHEMICAL EQUILIBRIUM IS ESTABLISHED WHEN THE FORWARD RATE EQUALS
THE REVERSE RATE.
FORWARD RATE
A + B
C+D
REVERSE RATE
• 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.
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.
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
1) INCREASING A WILL CAUSE
MORE COLLISIONS BETWEEN A
AND B,
2) THE FORWARD RATE WILL
INCREASE.
3) A WILL INCREASE THEN
DECREASE AS IT IS REACTED.
4) B WILL DECREASE AS IT IS
REACTED (CONSUMED)
C+D
FORWARD RATE
1) THE FORWARD RATE IS
INCREASED PREFFERENTIALLY.
2) PRODUCTS C AND D
INCREASE.
3) AS C AND D INCREASE THE
COLLISIONS BETWEEN THEM
INCREASE.
4) THE REVERSE RATE INCREASES
UNTIL THE RATES ARE EQUAL
AND A NEW EQUILBRIUM IS
ESTABLISHED
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:
REVERSE RATE
1) THE REVERSE RATE IS
INCREASED PREFFERENTIALLY.
2) REACTANTS A AND B
INCREASE.
3) AS A AND B INCREASE THE
COLLISIONS BETWEEN THEM
INCREASE.
4) THE FORWARD RATE INCREASES
UNTILL THE RATES ARE EQUAL
AND A NEW EQUILBRIUM IS
ESTABLISHED
A+B
C+D
1) INCREASING C WILL CAUSE
MORE COLLISIONS BETWEEN C
AND D,
2) THE REVERSE RATE WILL
INCREASE.
3) C WILL INCREASE THEN
DECREASE AS IT IS REACTED.
4) D WILL DECREASE AS IT IS
REACTED (CONSUMED)
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:
FORWARD RATE
1) THE REVERSE RATE IS
DECREASED PREFFERENTIALLY.
2) REACTANTS A AND B
DECREASE.
3) AS A AND B DECREASE THE
COLLISIONS BETWEEN THEM
DECREASE.
4) THE FORWARD RATE
DECREASES UNTILL THE RATES
ARE EQUAL AND A NEW
EQUILBRIUM IS ESTABLISHED
A+B
C+D
1) DECREASING C WILL CAUSE
LESS COLLISIONS BETWEEN C
AND D,
2) THE REVERSE RATE WILL
DECREASE, FORWARD IS NOW
FASTER.
3) C WILL DECREASE THEN
INCREASE..
4) D WILL INCREASEAS IT IS
PRODUCED.
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:
REVERSE RATE
1) DECREASING A WILL CAUSE
LESS COLLISIONS BETWEEN A
AND B,
2) THE FORWARD RATE WILL
DECREASE, REVERSE IS NOW
FASTER.
3) A WILL DECREASE THEN
INCREASE..
4) B WILL INCREASEAS IT IS
PRODUCED.
A+B
C+D
1) THE FORWARD RATE IS
DECREASED PREFFERENTIALLY.
2) PRODUCTS C AND D
DECREASE.
3) AS C AND D DECREASE THE
COLLISIONS BETWEEN THEM
DECREASE.
4) THE REVERSE RATE DECREASES
UNTILL THE RATES ARE EQUAL
AND A NEW EQUILBRIUM IS
ESTABLISHED
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
1) THERE ARE 2 TOTAL MOLESOF GAS ON
THIS SIDE.
2) MORE GAS COLLISIONS PUSH THE
REACTION TO THE OPPOSITE SIDE,
FORWARD IN THIS REACTION.
3) 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
1) THE ONE MOLE OF GAS
OCCUPIES LESS VOLUME,
ACCORDING TO BOYLE THAT IS
LOGICAL….SHIFT TO THIS SIDE.
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
1) THERE ARE 2 TOTAL MOLESOF GAS ON
THIS SIDE.
2) 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.
1) 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.