Equilibrium Unit 6 Chemistry Spring 15

Agenda 5/1 Equilibrium Game Happy Prom Weekend!!

Equilibrium Game A  B Reaction Cylinder A Cylinder B One straw Cylinder B Other straw Equilibrium is reached when volume in each tube is no longer changing during transfers

Agenda 5/4/15 Warm-Up Equilibrium Game conclusion Questions Notes: Intro to Equilibrium Conclusion: Equilibrium Game HW: None

May the 4th be with you

Stoich Review If a reaction requires 10.0g of bromine gas at STP, how many liters of bromine would this reaction use?

Equilibrium What is equilibrium? Equilibrium Game 1. Level of water in each cylinder stays CONSTANT 2. Rate of water transfer to A = Rate of water transfer to B *EQUAL RATES of transfer between reactants and products* NOT equal amounts!!

Equilibrium 2. Opposite processes at equal rates Reactants  Products Characteristics of Equilibrium 1. Constant property vapor pressure concentration of soln levels of H2O Colors 2. Opposite processes at equal rates Reactants  Products

Equilibrium Requirements to Maintain Equilibrium 1. Reversible process or reaction () 2. Closed system - nothing added or removed (not necessarily sealed except for gases) 3. Constant T

Equilibrium Altering Equilibrium “stress” or change occurs Equilibrium Game A B 1. Alteration or change -- also called disturbance or stress How did adding more H2O change the amount of B?

Equilibrium 2. Effect on Equilibrium System a) system reacted by increasing amount of H2O in B (right side, products) b) new equilibrium was achieved sooner now more water in A and B some of added water was transferred to B, but not all of it

Agenda 5/05/15 Collect: Equilibrium Conclusion Le Chatlier’s Lab Notes: Le Chat’s Principle HW: Complete Lab Write Up

Revenge of the Fifth

Warm- UP What is the pressure in atm of a .200 mol of gas that has a volume of 2.5L and is at 23 degrees celsius?

Agenda 5/6/15 Warm-Up Hand Back Equilibrium Tests Conclude Le Chat Lab Collect Notes: Le Chat’s Principle

Warm-Up If you have a solution that contains 15.0g of NaCl in 125mL of water, what is the molarity of the solution?

Le Chatlier’s Principle What is Le Chat’s Principle and how can it be used to determine the changes in an equilibrium?

Equilibrium LeChatelier’s Principle If an equilibrium is subjected to a stress, the equilibrium is shifted in the direction that relieves the stress

Equilibrium Post Lab - Disturbing the Equil. Expt. 1. Concentration a. Increase conc. on one side of eqn. -- shift to opposite side of eqn. b. Decrease conc. Or removal due to reaction w/ a substance on one side of the eqn. -- shift to same side of eqn.

Equilibrium 2. Temp Change (heating/cooling) a. Increase heat on one side -- shift to opposite side b. Decrease heat on one side -- shift to same side

Equilibrium What happens: Equilibrium means the reaction is HAPPY! :D Increased reactants cause forward rate to be faster (Products get jealous) More products are formed (to make up for jealousy) Eventually -- rates equal out -- new equilibrium HAPPY AGAIN!!

Equilibrium What happens: Decreased reactants cause forward rate to slow down (Reactants get jealous) More reactants are formed (to make up for jealousy) Eventually -- rates equal out -- new equilibrium HAPPY AGAIN!!

Equilibrium Key: ____ stress, change, alteration, disturbance ____ increase in concentration or heat ____ decrease in concentration or heat (also removal or reaction of substance removing it) ____ shift to right side of equation ____ shift to left side of equation s

Equilibrium Stress Equilibrium Shift Examples: Cu (s) + 2Ag+ (aq) Cu2+ (aq) + 2Ag (s) Ag+ s Add Cl- Ag+ + Cl- s AgCl Rxn removes Ag+

Equilibrium Example 2: Stress N2O4 (g) + Heat 2NO2 (g) Heat (increase T) s Cool (Remove heat) s

Agenda 5/7/15 Warm-Up Notes: Le Chat Notes: Equilibrium Constants Thermodynamics Notes: Le Chat More Practice Problems Notes: Equilibrium Constants Practice Writing and Using K Expressions TEST MONDAY

Warm-Up A 2.0 g sample of water is heated. Its temperature is changed by 86 degrees Celsius. How much heat was gained by the water?

Equilibrium Effects on a Gas at Equilibrium 2 H2 (g) + O2 (g) < 2 H2O(g) Decreasing volume (increasing pressure) Cause a shift to the side that takes up less space Increase volume (decrease pressure) Cause a shift toward side that takes up more space

Increase in volume is like…

Equilibrium Stress Reddish- brown N2O4 (g) + Heat 2NO2 (g) colorless System wants to decrease pressure Increasing P by decreasing V by forming less molecules System wants to increase pressure Decreasing P by increasing V by forming more molecules

*Remember - P and V of gases are inversely proportional!* Equilibrium Strategy for gases: Count the total # of gaseous molecules on each side (remember: s, l, aq not changed by P) Increased V means more room for gas. The system uses this room. (Decrease in P) Decreased V means less room for gas. The system makes up for this. (Increased P) If stress is listed as increased or decreased P, reinterpret as change in V and solve as listed in #1-3. *Remember - P and V of gases are inversely proportional!*

Equilibrium Effect of Catalyst on Equilibrium Catalyst increases rate of reaction Increases BOTH forward and reverse reactions Net effect: no shift -- no changes in concentration Reaches equilibrium faster

Equilibrium Expressions How can you write an equilibrium expression and how can you use it to determine a shift in equilibrium?

Quantitative Aspects of Equilibrium Equilibrium Constant Expression Definition - mathematical expression of concentrations of products and reactants that results in a constant ratio

Quantitative Aspects of Equilibrium The General Form: Keq = [products] [reactants] Example: N2 (g) + 3H2 (g) 2NH3 (g) Keq = [NH3]2 [N2][H2]3

Quantitative Aspects of Equilibrium Rules for Writing Equil. Constant Expression Equations Each product on top in a [] Each reactant on bottom in a [] Coefficients from chemical equation become exponents on the [] in the equil. equation Concentration of liquids and solids are NOT included in the equil. eqn. -- leave out (s) and (l)

Quantitative Aspects of Equilibrium Examples: N2 (g) + 3H2 (g) 2NH3 (g) Keq = [NH3]2 [N2][H2]3

Quantitative Aspects of Equilibrium PbCl2(s) Pb2+(aq) + 2Cl-(aq) Keq = [Pb2+][Cl-]2 HCl(g) + H2O(l) H3O+(aq) + Cl-(aq) Keq = [H3O+][Cl-] [HCl]

Quantitative Aspects of Equilibrium Simple Calculations using Equilibrium Constant Expression Equations See Handout…

Quantitative Aspects of Equilibrium Significance of the Magnitude (Size) of the Values for the Equilibrium Constant Keq = [products] [reactants] If Keq > 1: Products of the reaction are favored If Keq < 1: Reactants of the reaction are favored

Quantitative Aspects of Equilibrium Examples: Large equil constant -- greater than 1.0 A B Keq = 120 Keq = [B] [A] Ratio: 120 = [B] 1 [A]

Quantitative Aspects of Equilibrium 2. Small equil constant -- less than 1.0 C D Keq = 2.5x10-10 Keq = [D] [C] Ratio: 2.5x10-10 = [D] 1 [C]