1. Unit 7 Test = ___%

2. I studied by …

3. Next time I will study by…

4. We will reevaluate our goals momentarily…

Day 1 3-11

period 3

4. Reevaluating your goal:

Calculate your average on the 7 tests we’ve taken (use your tests or your goal setting ATBs to get grades).

Record your average. Test average so far = ____

Record your new goal (you must improve upon your average by at least 2 percentage points (or one if your average is an A)).

Day 1 3-11

period 3

1. Unit 7 Test = ___%

2. I studied by …

3. Next time I will study by…

4. We will reevaluate our goals momentarily…

Day 2 3-12

period 1

4. Reevaluating your goal:

Calculate your average on the 7 tests we’ve taken (use your tests or your goal setting ATBs to get grades).

Record your average. Test average so far = ____

Record your new goal (you must improve upon your average by at least 2 percentage points (or one if your average is an A)).

Day 2 3-12

period 1

Question of the Day

ΔG determines whether or not a reaction will _____,

but even a spontaneous reaction can be very _________.

Day 1 3-11 pd 3

GO

SLOW

Objective

How fast / slow do reactions go?

Reaction RatesIntro. to Rxn Rates & Collision Theory:

Rates of reaction determine how fast a reaction goes.

Usually expressed as the change in amount of reactant or product per unit time (moles / unit time)

Reaction RatesCollision Theory: = atoms, ions, and molecules can

react to form products, if and only if, they collide with enough kinetic energy.

If they do not have enough kinetic energy to react they bounce apart unchanged.

Reaction RatesCollision Theory:

The minimum energy that colliding particles must have to react is called activation energy.

Reaction Rates

Reaction RatesFactors Affecting Rxn Rates:

1. Temperature

at higher temps. particles move faster and so frequency of collisions increases along with the kinetic energy of particles… activation energy overcome easier

Reaction RatesFactors Affecting Rxn Rates:

2. Concentration increasing concentration increases

frequency of collision… activation energy overcome easier

Reaction RatesFactors Affecting Rxn Rates:

3. Particle size smaller particle size = greater surface

area and so more reactant available for reaction so frequency of collisions increases… activation energy overcome easier

Reaction RatesFactors Affecting Rxn Rates:

4. Catalyst

catalyst = a substance that speeds up the rate of reaction without being changed itself

a catalyst speeds up the reaction by helping the reactants reach their activated complex (by decreasing the needed activation energy)

Reaction RatesFactors Affecting Rxn Rates:

4. Catalyst

A catalyst is not changed during reaction, therefore it is NOT written as a reactant or product, but usually over the yield arrow:

2H2(g) + O2(g) 2H2O(g)Pt

Reaction Rates

Reaction Rates

Reaction Rates

II. The Progress of Chemical Reactions:

A. Chemical kinetics is the study of the rates of chemical reactions:

How fast will the reaction go?

B. Reaction rate is the change in concentration of reactant or product over time.

Reaction RatesII. The Progress of Chemical Reactions:

B. Reaction rate is the change in concentration of reactant or product over time.

1. Rxn rate CANNOT be determined by just looking at the chemical equation.

2. Formula:

Average Rate of Reaction = Δ[reactant]

ΔtOR

Δ[product]

Δt

Reaction Rates1. Rxn rate CANNOT be determined by just looking at the chemical equation.

2. Formula:

Average Rate of Reaction = Δ[reactant]

ΔtOR

Δ[product]

Δt

[ ] = concentration = M = moles/L

Question of the Day

Four factors that influence reaction rate = …

Day 6 4-11

AssignmentRead / review section 18.1 and complete #s 1-5 on page 601.

Reaction RatesII. The Progress of Chemical Reactions:

C. Rate Laws

rate law = an expression for the rate of a reaction in terms of the concentrations of reactantsRate = k[reactant1]x[reactant2]y

generic rate law

k = rate constant – temp. sensitive

x, y = order of rxn – how Δ[ ] affects rate – found through experimentation

Reaction Rates

II. The Progress of Chemical Reactions:

NOTE: k is large if the products form quickly and small if the products form slowly.

Reaction RatesII. The Progress of Chemical Reactions:

Reaction order from rate laws:

Rates can depend on different reactants in different ways.

If : x = 0 – the reaction is said to be zero order in reactant1 and the rate of reaction is independent of the concentration of reactant1

Reaction Rates

II. The Progress of Chemical Reactions:

x = 1 – the reaction is said to be first order in reactant1 and the rate is directly related to the concentration of reactant1

x = 2 – the reaction is said to be second order in reactant1 and the rate is dependent on the concentration of reactant1 squared.

Reaction RatesII. The Progress of Chemical Reactions:

Note: the overall order for a reaction is simply the individual orders for each reactant added together (a reaction that is first order in A and second order in B is third order overall).

Reaction RatesII. The Progress of Chemical Reactions:

Note: the overall order for a reaction is simply the individual orders for each reactant added together (a reaction that is first order in A and second order in B is third order overall).

formula to find order: ratenew

rateold

=concnew

concold( )

x

Reaction RatesExample: Consider the rxn A B. The rate law for this rxn is rate = k[A]x. From the data below, find the order of the rxn w/ respect to A and the overall order of the rxn.

TRIAL INITIAL CONCENTRATION

OF A (mol/L)INITIAL RATE (mol/(L*s))

1 0.050 3.0 * 10-4

2 0.10 12 * 10-4

3 0.20 48 * 10-4

ratenew

rateold

=concnew

concold( )

x

Reaction RatesHow about units for k?

units for k depend on the order of the reaction

units for the rate = concentration / time = M/s = mols/(L*s)

What would the units for k be if the reaction was first order overall?

Reaction RatesEXAMPLE: The following data were collected for the rate of disappearance of NO in the reaction:2NO(g) + O2(g) 2NO2(g)

Initial Rate Experiment

What is the rate law for the reaction and the value of the rate constant?

Experiment Number

[NO] (M) [O2] (M) initial rate (M/s)

1 0.0126 0.0125 1.41 x 10-2

2 0.0252 0.0250 1.13 x 10-1

3 0.0252 0.0125 5.64 x 10-2

Question of the DayDay 1 4-14

The data in the table below were obtained for the rxn:

a. The order of the reaction in A is ____. b. The order of the reaction in B is ____. c. The overall order of the reaction is ____.

A B P

02

2

Reaction RatesThe reaction 2NO + 2H2 N2 + 2H2O is first-order in H2 and second-order in NO. What happens to the rate when

(i) [NO] is doubled, while [H2] is fixed (ii) [NO] is fixed, while [H2] is doubled (iii) both [NO] and [H2] are doubled?

quadruplesdoublesX 8

Review

Suppose that for the reaction A + B → C, the rate law is rate = 3.0 x 10-5 [A][B]2.

What is the concentration of “B” if [A] = 0.10 M and the rate is 1.2 x 10-11 M/s?

There are no units on k, what should they be?

0.002 M

Rxn Mechanisms & Rate-Determining StepsA. A reaction mechanism is a series of ____________ that lead to a net reaction.

B. Reaction mechanisms can have _____________ steps.

C. Parts of mechanisms

1. Net reaction is _________

simple rxns

one or more

the goal

Rxn Mechanisms & Rate-Determining StepsC. Parts of mechanisms

1. Net reaction is __________

2. Elementary step is one of the __________ in the ________

3. Intermediate product is a product that is made by _______________ _____ that becomes a _________ in a subsequent ________________

the goal

reactions process

an elementarystep reactan

telementary step

Rxn Mechanisms & Rate-Determining StepsC. Parts of mechanisms

4. Catalyst is a substance that first appears as a _________ in one ________________ and then becomes a ________ in a subsequent ________________

reactantelementary stepproductelementary step

Reaction mechanisms that have multiple steps have one step that is the rate-determining step. The rate-determining step is the step that is the _______ of all the steps.

Rxn Mechanisms & Rate-Determining Steps

slowest

http://wps.prenhall.com/esm_brown_chemistry_9/2/660/169060.cw/index.html

Homework # 2 Chapter 14 – w/ discussion partner – show me successful screen (100%)

# 7 = the reaction rate would quadruple. doubling the partial pressure is the same as doubling the concentration.

Rate = k[A]x[B]y

Average Rate of Reaction = Δ[reactant]

ΔtOR

Δ[product]

Δt

[ ] = concentration = M = moles solute

liters solution

Average Rate of Reaction = OR

[ ] = = M =

Rate = k[reactant1]x[reactant2]y

Average Rate of Reaction = Δ[reactant]

ΔtOR

Δ[product]

Δt

[ ] = concentration = M = moles solute

liters solution

[ ] = = M =

generic rate law

k = rate constant – temp. sensitive

x, y = order of rxn – how Δ[ ] affects rate – found through experimentation

ratenew

rateold

=concnew

concold( )

x

liters solution

[ ] = = M =

A

B