Ch 18 Reaction RatesCh 18 Reaction Rates You have 5 minutesYou have 5 minutes Vocab outVocab out ½ sheet of paper½ sheet of paper A tablet will be dropped into hot water and A tablet will be dropped into hot water and

cold water.cold water. A powdered tablet will be dropped into hot A powdered tablet will be dropped into hot

water and cold water.water and cold water.

Rank the reactions in terms of speed of Rank the reactions in terms of speed of completion (1-4), which will be first and last completion (1-4), which will be first and last to complete. Explain, 3-4 sentences. to complete. Explain, 3-4 sentences.

10% per round reversible 10% per round reversible reactionreaction At the At the start of eachstart of each round 10% of A pennies are round 10% of A pennies are

passed to B while 10% of B pennies are passed to passed to B while 10% of B pennies are passed to A. (A. (DO NOT DO NOT PASS THEN COUNT 10%, count your pennies PASS THEN COUNT 10%, count your pennies at the start of each round and then pass at the start of each round and then pass them to the other pile, round to whole them to the other pile, round to whole numbers)numbers)

A starts with 100A starts with 100 B starts with 0B starts with 0 Create a table and graph that shows the pennies at Create a table and graph that shows the pennies at

the start of each round.the start of each round. Do 15 roundsDo 15 rounds You have 5 minutesYou have 5 minutes

10% / 20% reversible reaction10% / 20% reversible reaction At the At the start of eachstart of each round 10% of A round 10% of A

pennies are passed to B while 20% of B pennies are passed to B while 20% of B pennies are passed to A. pennies are passed to A. ( (DO NOT PASS THEN DO NOT PASS THEN COUNT 10%, count your pennies at COUNT 10%, count your pennies at the start of each round, round to the start of each round, round to whole numbers)whole numbers)

A starts with 100A starts with 100 B starts with 0B starts with 0 Create a table and graph that shows the Create a table and graph that shows the

pennies at the start of each round.pennies at the start of each round. Do 15 rounds, you have 5 minutesDo 15 rounds, you have 5 minutes

Reaction Rates and equilibrium

Rate = time interval that a Rate = time interval that a change occurs in (s, min, day…)change occurs in (s, min, day…)amount of reactant changing per unit time.amount of reactant changing per unit time.

Example Example g/hr ,g/hr , mol/s mol/s

Collision theoryCollision theory – when atoms, – when atoms, ions, molecules collide they ions, molecules collide they cancan

form a bond if the KE is high form a bond if the KE is high enough (and orientation is right)enough (and orientation is right) How can you increase KE?How can you increase KE?

activation energy= minimum energy colliding particles must have in order to react

Factors affecting reaction Factors affecting reaction ratesrates

Temperature - more Temperature - more collisions more energeticcollisions more energetic

(higher KE)(higher KE)

Does milk spoil in your Does milk spoil in your refrigerator?refrigerator?

Concentration – more Concentration – more particles usually more particles usually more

collisionscollisions

Particle size – usually more Particle size – usually more surface area equals more surface area equals more

collisions (smaller particles react collisions (smaller particles react faster)faster)

Catalyst- lowers the activation Catalyst- lowers the activation energy(more collisions are energy(more collisions are

effective) but does not react effective) but does not react itselfitself

Section 18.2 Reversible Section 18.2 Reversible reactions – react in both reactions – react in both

directions simultaneouslydirections simultaneously

Chemical equilibrium – Chemical equilibrium – forward and reverse reactions forward and reverse reactions take place at the same timetake place at the same time

Is the water Is the water in this bottle in this bottle evaporating?evaporating?

Factors that affect Factors that affect equilibriumequilibrium

Concentration, pressure, Concentration, pressure, temperature will cause a shift in temperature will cause a shift in

equilibrium equilibrium ex. More products formedex. More products formed

Le Châtelier’s principle: Le Châtelier’s principle: a a stress is applied to astress is applied to asystem in dynamic system in dynamic

equilibrium, the system equilibrium, the system changes to relieve the changes to relieve the

stress.stress.Ex. More products formedEx. More products formed

Predict the change in equilibrium Predict the change in equilibrium 1. Remove O1. Remove O22 2.2. Add OAdd O22 3. increase pressure3. increase pressure4. decrease pressure4. decrease pressure

Predict the change in equilibrium Predict the change in equilibrium 1. heat mixture 1. heat mixture 2.2. add SOadd SO22

3. remove SO3. remove SO33

4. cool mixture4. cool mixture

Equilibrium constantEquilibrium constantAre products or reactants Are products or reactants

favored?favored?Concentration [molarity…] Concentration [molarity…]

raised to the coefficientraised to the coefficient-products over reactants--products over reactants-

Keq >1 products are favoredKeq >1 products are favored

Keq < 1 reactants are favoredKeq < 1 reactants are favored

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

At equilibrium, aAt equilibrium, a5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, , 0.50 mol H0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

Calculate Calculate KKeqeq for the for the reaction.reaction.

Calculate molarity then use Calculate molarity then use the the equation to calculate the the equation to calculate

KKeqeq..

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

produces ammonia, which isproduces ammonia, which isa fertilizer. At equilibrium, aa fertilizer. At equilibrium, a

5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, 0.50 mol H, 0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

produces ammonia, which isproduces ammonia, which isa fertilizer. At equilibrium, aa fertilizer. At equilibrium, a

5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, 0.50 mol H, 0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

produces ammonia, which isproduces ammonia, which isa fertilizer. At equilibrium, aa fertilizer. At equilibrium, a

5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, 0.50 mol H, 0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

produces ammonia, which isproduces ammonia, which isa fertilizer. At equilibrium, aa fertilizer. At equilibrium, a

5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, 0.50 mol H, 0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

produces ammonia, which isproduces ammonia, which isa fertilizer. At equilibrium, aa fertilizer. At equilibrium, a

5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, 0.50 mol H, 0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

produces ammonia, which isproduces ammonia, which isa fertilizer. At equilibrium, aa fertilizer. At equilibrium, a

5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, 0.50 mol H, 0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

produces ammonia, which isproduces ammonia, which isa fertilizer. At equilibrium, aa fertilizer. At equilibrium, a

5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, 0.50 mol H, 0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

NN2(2(gg)) + 3H + 3H2(2(gg)) 2NH2NH3(3(gg))

produces ammonia, which isproduces ammonia, which isa fertilizer. At equilibrium, aa fertilizer. At equilibrium, a

5-L flask contains 0.30 mol N5-L flask contains 0.30 mol N22, 0.50 mol H, 0.50 mol H22, and 0.20 mol NH, and 0.20 mol NH33..

End day one notesEnd day one notes

1) Calculate the equilibrium constant 1) Calculate the equilibrium constant when 0.275 mol of SOwhen 0.275 mol of SO22 and 0.125 and 0.125 mol of Omol of O22 are in a 1.25L container are in a 1.25L container with 0.511 mol of SOwith 0.511 mol of SO33..

2a) Which way will the equilibrium 2a) Which way will the equilibrium shift if some Oshift if some O22 is removed? is removed?

2b) Which way will the equilibrium 2b) Which way will the equilibrium shift if the pressure is increased?shift if the pressure is increased?

Work/AnswersWork/Answers

1) 0.4088^2 / (.22^2 x 0.1)1) 0.4088^2 / (.22^2 x 0.1)0.16711744 / .00484 = keq = 34.50.16711744 / .00484 = keq = 34.5

Left, to replenish OLeft, to replenish O22

Right, less gas molesRight, less gas moles

Calculate the equilibrium constant Calculate the equilibrium constant when 0.275 mol of SOwhen 0.275 mol of SO22 and 0.125 and 0.125 mol of Omol of O22 are in a 1.00L container are in a 1.00L container with 0.511 mol of SOwith 0.511 mol of SO33..

If the pressure is increase what If the pressure is increase what amounts amounts in the previous problem would change?in the previous problem would change?

18.3 solubility 18.3 solubility equilibrium=Kequilibrium=Kspsp equilibrium of equilibrium of

insoluble saltsinsoluble saltsDROP THE SOLIDDROP THE SOLID

The The smaller the smaller the

KKspsp, the , the lower the lower the

solubility of solubility of the the

compound.compound.

What is the concentration ofWhat is the concentration ofCalcium ions in a saturatedCalcium ions in a saturated

CaSOCaSO44 solution at solution at100100C? (C? (KKspsp = = 4.5 x104.5 x10 -9-9))

CaSOCaSO44(s)(s) Ca Ca2+ 2+ (aq)(aq) + SO + SO44

2- 2- (aq)(aq)

common ion common ion = is found in = is found in both salts in a solutionboth salts in a solution

How would adding NaClHow would adding NaCl(aq)(aq) shift this reaction?shift this reaction?

common ion effectcommon ion effect= lowering of the solubility = lowering of the solubility of an ionic compound as a of an ionic compound as a result of the addition of a result of the addition of a

common ioncommon ion

What is the concentration ofWhat is the concentration ofsulfide ions in a 1.0-L sulfide ions in a 1.0-L

solutionsolutionof FeS to whichof FeS to which

0.04 mol of iron (II) chloride 0.04 mol of iron (II) chloride isis

added? added? The The KKsp of FeS is 8 xsp of FeS is 8 x 1010-19-19

18.4 entropy and free energy18.4 entropy and free energy

Free energy is the released Free energy is the released energy able to do workenergy able to do work

some of the energy some of the energy liberated inliberated in

chemical reaction can be chemical reaction can be harnessed to do work, harnessed to do work,

such as driving the pistonssuch as driving the pistonsof an internal-combustion of an internal-combustion

engine. engine.

The internal-combustion The internal-combustion engine in a car is only about engine in a car is only about 30% efficient; that is, only 30% efficient; that is, only

about 30% of the free about 30% of the free energyenergy

released by burning gasoline released by burning gasoline is used to propel the car.is used to propel the car.

Spontaneous Spontaneous reactions =reactions =substantial substantial amounts of amounts of products at products at equilibrium equilibrium and release and release free energyfree energy

nonspontaneous reaction nonspontaneous reaction = =

does not favor the formation does not favor the formation of products at the specified of products at the specified

conditionsconditions

Some reactions that are Some reactions that are spontaneous at one set of spontaneous at one set of

conditions mayconditions maynot be at anothernot be at another

law of disorder =law of disorder =the natural tendency is for the natural tendency is for

systems to move in the systems to move in the direction of maximum direction of maximum

disorderdisorder

What are the odds that a What are the odds that a tornado hit this room?tornado hit this room?

An increase in entropy An increase in entropy (more random) favors the (more random) favors the

spontaneous chemicalspontaneous chemicalreaction; as does a reaction; as does a

decrease in enthalpy decrease in enthalpy (exothermic)(exothermic)

The size and directionThe size and directionof enthalpy changes and of enthalpy changes and

entropy changes entropy changes together determine together determine

whether awhether areaction is spontaneousreaction is spontaneous

Spontaneous reactions Spontaneous reactions naturally favor the formation naturally favor the formation

of productsof products

Law of disorder – Things Law of disorder – Things move in the direction of move in the direction of

maximum entropy (disorder)maximum entropy (disorder)