Question of the Day

For a reaction involving a single reactant, the following data were obtained.

Day 2 4-15

Determine the order of the reaction. Either show work or explain!  

Question of the Day

Does an oreo get soggy quicker in milk or a milkshake? Explain the difference in reaction rate in terms of one of the four factors influencing reaction rates (BE SPECIFIC!)

Day 3 4-16

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.

Question of the DayThe following data were collected for the rate of disappearance

of NO in the reaction: 2NO(g) + O2(g) 2NO2(g)  

Write the rate law for this equation: _______________________ 

Solve for k: 

What are the units for k?

Day 5 4-22

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

Postlabs are due on Wednesday 4-23

Lab reports and presentations are due Friday 4-25

E. Write several mechanisms and identify any intermediates and catalysts.

1. 1-step mechanism for reaction of calcium oxide with water

Rxn Mechanisms & Rate-Determining Steps

Question of the DayDay 6 4-23

Describe how intermediates, activated complexes, and catalysts are different (thoroughly!).

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.

E. Write several mechanisms and identify any intermediates and catalysts.

2. 2-step mechanism for rxn of NO2 with CO to produce NO and CO2 (all gases)

Rxn Mechanisms & Rate-Determining Steps

NO2 + NO2 NO3 + NO

NO3 + CO NO2 + CO2

slow

fast

NO2 + CO NO + CO2 net

Period 1 stopped

4-22

2. 2-step mechanism for rxn of NO2 with CO to produce NO and CO2 (all gases)

Rxn Mechanisms & Rate-Determining Steps

NO2 + NO2 NO3 + NO

NO3 + CO NO2 + CO2

slow

fast

NO2 + CO NO + CO2 net

Intermediate =NO3

E. Write several mechanisms and identify any intermediates and catalysts.

3. 3-step mechanism for the rxn of HBr with O2 to produce H2O and Br2 (all gases)

Rxn Mechanisms & Rate-Determining Steps

HBr + O2 HOOBr

HBr + HOOBr 2 HOBr

2 HBr + 2 HOBr 2 H2O + 2 Br24 HBr + O2 2 H2O + 2 Br2

3. 3-step mechanism for the rxn of HBr with O2 to produce H2O and Br2 (all gases)

Rxn Mechanisms & Rate-Determining Steps

HBr + O2 HOOBr

HBr + HOOBr 2 HOBr

2 HBr + 2 HOBr 2 H2O + 2 Br24 HBr + O2 2 H2O + 2 Br2

Intermediates =HOOBr and HOBr

4. Write the net rxn for the following 2-step mechanism.

NO2(g) + SO2(g) → NO(g) + SO3(g)

2 NO(g) + O2(g) → 2 NO2(g)

Rxn Mechanisms & Rate-Determining Steps

ReviewAnalyze the following reaction mechanism:

step 1: N2O N2 + Ostep 2: N2O + O N2 + O2

What is the net reaction?

Are there any intermediates and/or catalysts present?

Equilibrium Equilibrium occurs when the forward and

reverse reactions occur at equal rates – NOT a standstill!

Equilibrium

A. Physical Equilibrium Example

1. H2O(l) ⇄ H2O(g)

2. Appearance of system

Rate of Evap. = Rate of Cond.Rate of Evap. = Rate of Cond.

To regular eyes: To regular eyes: Looks as if nothing is Looks as if nothing is happeninghappening

But on the molecular level: But on the molecular level: 2 rxns or 2 rxns or s occur s occur simultaneouslysimultaneously

B. Chemical Reaction Options

1. Rxn goes to completion products stay & reaction stops; Ex : burning 2. No go : He + Ne no rxn3. Rxn reaches equilibrium = get a set

amount of reactants & products coexisting

C. Main Concern of Equilibrium Calculations

1. How FAR will the reaction go?2. How much product can be made?

Equilibrium

D. What conditions must be met to attain equilibrium?

– Constant T & P– Closed container– G = 0

Equilibrium

E. Example equilibrium system and experimental data: 2 HI(g) I⇄ 2(g) + H2(g)

[HI] [I2] [H2] → [HI] [I2] [H2]

Exp #1 0.2 0 0 →

Exp #2 0 0.1 0.1 →

Exp #3 0.1 0.1 0.1 →

0.160.16 0.020.02 0.020.02

0.160.16 0.020.02 0.020.02

0.240.24 0.030.03 0.030.03

Equilibrium

• What happened to the concentrations of each substance during the experiments?

– Exp #1 & #2 •Changed to form chemicals not

present at the start of the reaction

– Exp #3•Changed to form more of the “favored” chemicals

Equilibrium

C. Example of system reaching equilibrium

N2O4(g) ⇄ 2 NO2(g) at 100 °C

Time (s) 0 20 40 60 80 100

[N2O4] 0.100 0.070 0.050 0.040 0.040 0.040

[NO2] 0.000 0.060 0.100 0.120 0.120 0.120

Equilibrium

Stopped on 4-2

Assignment:

Review section 18.2 and complete #s 9-16 on page 608.

Period # 1 LAB

http://chemconnections.org/Java/equilibrium/index.html

http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animations/equilvpBr2V8.html

Equilibrium