Transcript Equilibrium
Chemistry 1. 2. 3. 4. 5. No Warm-Up Today Please take out your Calculating Keq Lab response sheet Get into your lab groups Get out one piece of paper per group Make sure you have a calculator! Partner Practice Quiz: Calculating Keq Lab Fe+3(aq) + SCN-(aq) ↔ FeSCN+2(aq) The reaction starts with 6.0mL of 0.0040M Fe(NO3)3 and 4.0 mL of 0.0030M KSCN. Using a colorimeter you test the absorbance of FeSCN+2 at equilibrium = 0.318. A “standard” is measured, which has a concentration of 0.0006M and absorbance of 0.802. 1. What is the initial concentration all chemicals in the test tube?(Hint: M1V1….) 2. What is the concentration of FeSCN+2 at equilibrium? (Hint: Beer’s Law) 3. Calculate the concentrations of Fe+3 & SCN- at equilibrium. (Hint: IceBox) 4. Calculate the Keq for this reaction. (Hint: Write equilibrium expression and plug it in) TRADE AND GRADE! ANS Group Quiz Calcs Fe+3(aq) + SCN-(aq) FeSCN+2(aq) The reaction starts with: 6.0mL of 0.0040M Fe(NO3)3 + 4.0 mL of 0.0030M KSCN. The absorbance of FeSCN+2 at equilibrium = 0.318. A 0.0006 M “standard” has an eq. absorbance of 0.802. Calculate the Keq for this reaction. Please turn in your lab to inbox. You may keep it and turn it in next class if you need to make corrections Le Châtelier’s Principle Can we predict the effects of concentration, pressure, volume, and temperature on a system at equilibrium? (More importantly: can we manipulate a chemical reaction to make more product and thus more $$$$$)? Le Châtelier’s Principle Human blood has a certain pH.When people exercise they products a lot of carbon dioxide, which in turn builds up carbonic acid in their bodies. Carbonic acid alters the pH of the blood, which puts stress on the body. How does the body return to a healthy equilibrium? Le Châtelier’s Principle If you change the conditions of a reaction to affect the equilibrium of a system, then reaction shifts in a direction that reduces the effect of that change Stress Reaction = Reaction Shifts to Relieve Stress. You can change: ◦ Concentration ◦ Temperature ◦ Pressure/Volume ADD AWAY Take Towards Exploring Equilibrium & Le Châtelier’s Principle Grab one computer for you and a partner (1 per partnership) Log in to the computer Read along as I read aloud! Le Châtelier’s “Mini-Lab” Questions to think about: What happens if you increase the concentration of reactants? What happens if you increase the concentration of products? What happens when you increase the temperature? What happens when you decrease the temperature? Work with your partner to complete Trials 1-6 Process the data that you recorded by completing the “conclusion” on the back We will review, by taking notes LE CHÂTELIER’S PRINCIPLE NOTES Le Châtelier’s Principle If you change the conditions of a reaction to affect the equilibrium of a system, then reaction shifts in a direction that reduces the effect of that change Stress Reaction = Reaction Shifts to Relieve Stress. You Can change: ◦ Concentration ◦ Temperature ◦ Pressure/Volume ADD AWAY Take Towards Le Châtelier’s: Change in Concentration (1-2) Adding more reactant will increase rate of forward reaction because more collisions are occurring, forming more product. After additional reactant is added, the system will return to equilibrium after enough time What would happen if you took away reactant instead? ◦ Reaction shifts left to replace the reactants that were taken away! ◦ Giving the products more room to hit each other and form more reactants! Le Châtelier’s: Change in Concentration (3-4) Adding more product will increase rate of the reverse reaction because more collisions are occurring, forming more reactant. After additional product is added, the system will return to equilibrium after enough time What would happen if you took away product instead? ◦ Reaction shifts right to replace the products that were taken away! ◦ Giving the reactants more room to hit each other and form more products! Change in Temperature (5) Endothermic reactions: treat heat as a reactant N2(g) + O2(g) + heat ↔ 2NO(g) Adding heat will cause formation of more product. Shifts in the direction that consumes energy (increase in potential energy) Change in Temperature (6) Change in T can change the Keq of a reaction (unlike change in [ ], P,V) Exothermic reactions: treat heat as a product C(s) + O2(g) ↔ CO2(g) + heat Adding heat will cause formation of reactants (reaction shifts left) Effects of change in Volume/Pressure Decreased volume leads to increased pressure (Boyle’s Law) System moves to decrease # of gas molecules, thus decreasing pressure If V is increased, P decreases. The system will shift to bring P back up. Effects of change in V/P practice What happens when volume is reduced? P4(s) + 6Cl2(g)↔ 4PCl3(l) (6 gas molecules) (0 gas molecules) Solid and liquid don’t count! Reaction will form more product because the Cl2 molecules will be colliding more. This will shift to the right to lower pressure, forming more product! Effects of change in V/P example What happens when volume is increased? CO(g) + 2H2(g) ↔ CH3OH(g) (3 gas molecules) (1 gas molecule) Reaction will form more reactant because the only way to equalize pressure is to make more gas molecules. More Le Châtelier’s Practice Due Wednesday: Le Châtelier and Keq Worksheet 4-12 Upcoming Week (AP Testers) BLUE Wednesday, 5/6: Due: Châtelier’s and Keq Worksheet 4-12 In class: Concentration Effects Lab, Reaction Eq WS, Notes on Haber Method, Friday, 5/8: Due: Reaction Eq WS, Conc. Effects Lab In class: Test Review Tuesday, 5/12: Due: Test Review and any late work from the unit In Class: Equilibrium Unit Test You must be prepared for the unit test (no extensions!) You will need to turn in everything except the Conc. Effects Lab (excused) by 5/12. Upcoming Week (AP Testers) GOLD Thursday, 5/7: Due: Châtelier’s and Keq Worksheet 4-12 In class: Concentration Effects Lab, Reaction Eq WS, Notes on Haber Method, Monday, 5/11: Due: Reaction Eq WS, Conc. Effects Lab In class: Test Review Wednesday, 5/13: Due: Test Review and any late work from the unit In Class: Equilibrium Unit Test You must be prepared for the unit test (no extensions!) You will need to turn in everything except the Conc. Effects Lab (excused) by 5/13.