+ DMA 4/11/11 Write the balanced chemical equation for the reaction of aluminum and hydrochloric...

+

DMA 4/11/11

Write the balanced chemical equation for the reaction of aluminum and hydrochloric acid (HCl) to produce aluminum chloride and hydrogen gas.

+DMA - Monday, May 04, 2009

List three ways you might increase the rate of a chemical reaction? Give some examples.

+Tuesday, April 12, 2011

ClassNotes - Rates of Reactions

HomeworkNotes and Section Review Chapter 22

+

DMA 4/12/11

Get your notebook and a pencil and get ready to take some notes!

+

DMA 4/12/11

Name 2 things you think could increase the rate at which a chemical reaction happens.

+ Chemical KineticsThe area of chemistry that concerns reaction rates.

+ Chemical Kinetics

The area of chemistry concerned with the speed at which reactions occur is called chemical kinetics.

Reaction rate is the change in concentration of reactants and products in a certain amount of time.

Average rate of reaction = Δ [reactant or product]

Δ time

+ Collision Theory

Key Idea: Molecules must collide to react.

•In order to react molecules and atoms must

come in contact with each other.

•They must hit each other hard enough to react.

•Anything that increase these things will make

the reaction faster.

Ene

rgy

Reaction coordinate

Reactants

Products

Ene

rgy

Reaction coordinate

Reactants

Products

Activation Energy - Minimum energy to make the reaction happen

Ene

rgy

Reaction coordinate

Reactants

Products

Overall energy change

+ Endothermic Reactions

+ Exothermic Reactions

+

Pt surface

HH

HH

HH

HH

Hydrogen bonds to surface of metal.

Break H-H bonds

Catalysts

+

Pt surface

HH

HH

Catalysts

C HH C

HH

+

Pt surface

HH

HH

Catalysts

C HH C

HH

The double bond breaks and bonds to the catalyst.

+

Pt surface

HH

HH

Catalysts

C HH C

HH

The hydrogen atoms bond with the carbon

+

Pt surface

H

Catalysts

C HH C

HH

H HH

+Catalysts

+ Exothermic Reaction with a Catalyst

+ Endothermic Reaction witha Catalyst

+

DMA 4/13/11

What is a catalyst? How does it affect a chemical reaction?

Remember to turn in your homework!

+Your To-Do List for Today

Work independently and quietly!

In your books: Read & take notes on “Reaction Rates” on

pg. 722-724 Answer Question #1 on pg 731 Read & take notes on 22-2 on pg. 732-737 Answer Questions #1,2,5 on pg. 737 Read & take notes on 22-3 on pg. 738-743 Answer Questions #1-3

DUE TOMORROW!!

+

DMA 4/14/11

Explain the collision theory.

+To Do Today

Lab activity

Do the lab as written

Then, rerun the lab and time itCalculate the rate of the 2 reactions reactant/ time

Due at the end of Class today

Yesterday’s assignment is due tomorrow.

+

DMA 4/15/11

Name 2 reasons why a scientist would want to change the rate of a reaction. How could that scientist accomplish this?

+

DMA 4/18/11

Chlorine gas reacts with solid sodium to produce solid sodium chloride. If 4.85 L of chlorine gas at 308 K and 1.05 atm react with sodium, how many grams of sodium chloride are produced?

+

DMA 4/19/11

Get out your pre-labSit with your lab group

+

To Do Before you Start your lab:

1.Exchange your pre-lab with one

person.

2.Grade the other person’s lab

according to the rubric.

3.Get your pre-lab back from who

graded yours and fix anything that is

missing.

4.Bring your pre-labs to me in your lab

groups and I will approve you to begin

the lab.

+

If you were approved to begin yesterday:

Get your lab equipment and try to get a couple of trials done.

If you did not get your notebook stamped yesterday:

Make sure your pre-lab is done and get it to me for approval so you can begin running your lab.

DMA 4/20/11

+

Define the following:activation energycatalyst

DMA 4/21/11

+In the Lab today

If you were already approved to begin: Get your lab equipment and get all 10 of your

trials done. Be sure to keep careful track of your data You need the change in products(gas) and

change in time to calculate the rate of the reaction.

If you did not get your notebook stamped yet: Make sure your pre-lab is done and get it to me

for approval so you can begin running your lab.

+

DMA #1 4/22/11

What are the seven diatomic molecules? Why is it important to know what these are?

+Post Lab Lab Due Tuesday From your “Composition Book Data Collection Format”

Discussion of data collection

Graph-I want you to create a graph and attach it into your lab notebook. The graph should have your manipulated variable on the

x-axis and your responding variable (rate of reaction) on the y-axis

This can be done by hand or computer

Calculations of rates of reaction should be present

Lab question: answer this as part of your conclusion (the question asked at the beginning of the lab)

Conclusion: Claim, Evidence (data), Explain, Conclude

+Rate of Reaction Experiments

You will design, conduct, analyze, and report on how the rate of a chemical reaction is affected by the factors listed in the next column

You are expected to design your own experiments, not copy those of other lab groups.

You will need to collect 5 data points for each experiment.

1. Type of reactant

2. Temperature

3. Concentration of reactant

+How can we measure the rate of a reaction? In math: rate = distance/time

In life: rate = anything changing/time

How can we measure the rate of the reaction:

Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

Measure the zinc consumption or gas production versus time.

Draw & observe the standard set up for this lab.

+

Standard Reaction Rate Set Up

beaker

Test-tube

Rubber tubing

One-hole stopper 10ml graduated cylinderGlass tube

+Data & ObservationsKeep Track of?

Mass of Metal Used for Each Trial (1.0g max)

Amount of Acid Used for Each Trial (10 ml max)

Temperature (50C max, don’t try to be exact)

Time Elapsed for Each Trial (5 minute max)

Volume of Gas Produced for Each Trial (10ml max)

Observations for Each Trial

+Pre Lab Assignment:Question: “What is the effect of _____ on the

reaction rate of hydrochloric acid and a particular metal?”

Hypothesis:  (If, then, because)Manipulated Variable:Responding Variable:Controlled Variables:Materials:         Diagram:Validity Measure: (Calibrate? Prevent Contamination?)

Procedure: (at least 5 levels, repeated at least 2x)

+Experimental Controls?

Amount of Acid?

Strength of acid?

Amount of Metal?

When will you stop the trial?

+

+ Factors Affecting Rate

TemperatureIncreasing temperature always

increases the rate of a reaction. Surface Area

Increasing surface area increases the rate of a reaction Concentration

Increasing concentration USUALLY increases the rate of a reaction Presence of Catalysts

+Factors Affecting Rate

What are some real world examples for temperature? surface Area?concentration?presence of Catalysts?

+ CatalysisCatalyst: A substance that speeds up a reaction without being consumed

Enzyme: A large molecule (usually a protein) that catalyzes biological reactions.

Homogeneous catalyst: Present in the same phase as the reacting molecules.

Heterogeneous catalyst: Present in a different phase than the reacting molecules.

+ Catalysts Increase the Number of Effective Collisions

+ Energy Diagrams

1. Draw and label an energy diagram. Calculate the activation energy and change in energy of the reaction• Reactants – 78.9 kJ• Production – 125.3 kJ• Activated complex – 300 kJ

• Reactants - 25.1 kJ• Products – 35.2 kJ• Activated complex – 49.0 kJ

+ Collision Model

Orientation of reactants must allow formation of new bonds.

Collisions must have enough energy to produce the reaction (must equal or exceed the activation energy).

+2NO2(g) 2NO(g) + O2(g) Reaction Rates:

2. Can measure appearance of products

1. Can measure disappearance of reactants

3. Are proportional stoichiometrically

+ Rate of Reaction Lab

Rate of Reaction Lab

Introduction explain the collision theory and factors affect

the rate of the reaction describe how you will investigate your

condition how the collision theory and rate of reaction

relates to the real world. chemical reaction

Hypothesis

Variables

Procedure

+ DMA - Test Thursday

What is the collision theory?

What is an energy diagram?

What is an endothermic reaction?

What is an exothermic reaction?

What is activation energy?

What is a catalyst?

How do catalysis affect energy diagrams?

What factors affect the rate of the reaction?

+Reversible Reactions

In some chemical reactions, it is possible for the products to react and regenerate the reactants.

[Co(H2O)6]2+

(aq) + 4Cl-(aq) [CoCl4]2-

(aq) + 6H2O(l)

pink blue

+

Use rate of reaction to explain how you can tell if a chemical reaction has reached chemical equilibria.

Equilibrium exists when two opposing processes occur at the same rate.

Even though changes are occuring, there is no overall, or net, change.

Equilibria exists when the rate of forward reaction is equal to the rate of reverse reaction.

Equilibria

+Le Châtelier’s Principle

In 1888, a French mining engineer named Henri Louis le Châtelier discovered something about what happens when a reaction at equilibrium is disturbed.

Le Châteleier’s Principle: if a change in conditions is imposed on a system at equilibrium, the equilibrium position will shift in the direction that tends to reduce that change in conditions.

Le Châtelier’s Principle

If you introduce a change into a system at

equilibrium, the system will shift away from

the change to reestablish equilibrium.

What are two ways

to reestablish

equilibrium on this

teeter totter?

+Le Châtelier’s Principle

Reactions that reestablish equilibrium shift either to the right (make more products) or to the left (lose products, form reactants).

Adding reactants shift to the right.

Adding products shift to the left.

+Le Châtelier’s Principle

Removing chemicals

also causes a reaction

to have to shift to

reestablish equilibrium.

Remove products,

shift right.

Remove reactants,

shift left.

+ Le Châtelier’s Principle

There are other ways to force an reaction to

reestablish equilibrium.

Increasing pressure on one side of a reaction

is analogous to increasing concentration of chemicals.

Decreasing pressure on one side of a reaction is

analogous to decreasing concentration of chemicals.

+Exothermic/Endothermic Reactions

Exothermic reactions produce heat as a product in addition to the chemical products.

Endothermic reactions absorb heat as a reactant in addition to the chemical reactants.

Adding or removing heat from some reactions can force the reaction to shift and reestablish equilibrium.

The Haber Process

In 1913, the German scientist Fritz Haber utilized Le Châtelier’s Principle in a process for making ammonia from nitrogen and hydrogen.

Ammonia was used in the manufacture of explosives.

The Haber process allowed the Germans to continue manufacturing explosives despite a blockade on necessary materials by German opponents in WWI. Haber Einstein

Berlin 1914

Which way will equilibrium shift if the highlighted chemical is increased.1. NO2(g) N2O4(g)

2. N2(g) + H2(g) NH3(g)

3. COCl2(g) CO(g) + Cl2(g)

4. H2(g) + I2(g) HI(g)

5. C(s) + H2O(g) CO(g) + H2(g)

6. ZnCO3(s) ZnO(s) + CO2 (g)

7. NH4Cl(s) NH3(g) + HCl(g)

8. SO2(g) + O2(g) SO3(g)

9. CO(g) + H2(g) CH4(g) + H2O(g)

10. NaHCO3(s) + HCl(aq) H2O(l) + CO2(g) +NaCl(aq)

Which way will equilibrium shift if the highlighted chemical is decreased.•NO2(g) N2O4(g)

•N2(g) + H2(g) NH3(g)

•COCl2(g) CO(g) + Cl2(g)

•H2(g) + I2(g) HI(g)

•C(s) + H2O(g) CO(g) + H2(g)

•ZnCO3(s) ZnO(s) + CO2 (g)

•NH4Cl(s) NH3(g) + HCl(g)

•SO2(g) + O2(g) SO3(g)

•CO(g) + H2(g) CH4(g) + H2O(g)

•NaHCO3(s) + HCl(aq) H2O(l) + CO2(g) +NaCl(aq)

+Chemistry DMA 5/7

List three things that you could do to a chemical reaction at equilibrium to disrupt the system.

The Law of Chemical Equilibria

In 1864, Norwegian chemists Cato Maximillian Guldberg and Peter Waage formulated the Law of Mass Action that describes equilibrium.

They established an Equilibrium Expression and an Equilibrium Constant,

Guldberg Waage

+

aA + bB cC + dD

Keq = [C]c[D]d

[A]a[B]b

+

CO(g) + 3H2(g) CH4(g) + H2O(g)

Keq = [C]c[D]d

[A]a[B]b

Keq = [CH4][H2O]

[CO][H2]3

+Homogenous and Heterogeneous Equilibria

Homogenous equilibria occurs when all reactants and products are in the same physical state.

Heterogeneous equilibria occurs when reactants and products occurs in different physical states.

+Heterogeneous Equilibria

NH4NO3(s) N2O(g) + 2H2O(g)

Keq = [N2O][H2O]2

+Equilibrium Constant

Keq >> 1 at equilibrium, the system consists mostly of products.

Keq = 1 at equilibrium, the system contains roughly equal portions of products and reactants.

Keq << 1 at equilibrium, the system consists mostly of reactants.

+Write equilibrium expressions for each of the following equations:

1. NO2(g) N2O4(g)

2. N2(g) + H2(g) NH3(g)

3. COCl2(g) CO(g) + Cl2(g)

4. H2(g) + I2(g) HI(g)

5. C(s) + H2O(g) CO(g) + H2(g)

6. ZnCO3(s) ZnO(s) + CO2 (g)

7. NH4Cl(s) NH3(g) + HCl(g)

8. SO2(g) + O2(g) SO3(g)

9. CO(g) + H2(g) CH4(g) + H2O(g)

10. NaHCO3(s) + HCl(aq) H2O(l) + CO2(g) +NaCl(aq)

+

DMA 4/25/11

Name 4 things that can change the rate of a reaction.

+To Do Today

Turn in Ch 22 notes & questions

Work on 22-3 review (tomorrow’s quiz will be similar to this)

Create a graph- “Heating Curves”

14-4 read, take notes, answer questions #1-5

Remember, Rates of Reactions Lab is due tomorrow

+

DMA 4/26/11

Turn in your homework:1.Ch 22 notes &

questions2.Rates of Reactions Lab3.22-3 Review

+What are molecules doing in each phase?—Sketch the containers and add a description of the molecular motion of each.

What happens to each when heated?

+Phase Changes

Phases at the molecular level

Change of phase-the conversion of a substance from

one state of matter into anotherAlways involves a change in energy

+Phase Changes

+Phase Changes

Solid → Liquid →Gas

Heat of Fusion: Heat required to convert a solid at its melting point to a liquid

Heat of Vaporization: Heat required to convert a liquid at its boiling point to a gas.

Heat of Sublimation: Heat required to take a substance directly from its solid to its gas state

+ 5 Types of Energy Kinetic

The energy of motion

Potential Stored energy

Chemical energy inherent in the chemical bonds which hold molecules

together. Examples are coal and oil, which have energy potential that is released upon combustion.

Thermal/heat the kinetic energy of molecular motion. Measured as

temperature and perceived as heat.

Nuclear The energy stored in the nucleus of an atom.

+To Do

Complete the “Phase Change” graphing activity2 graphs-water and ammonia

Do not write on the assignment sheet-only on your graph paper

Return the data sheet at the end of class

+ Phase Change Diagram - WaterNote that the temperature of a substance does not change as it is going through a phase change.

+Calculating Energy Changes - Heating Curve for Water

Tem

pera

ture

(o C

)

40

20

0

-20

-40

-60

-80

-100

120

100

80

60

140

Time

DH = mol x DHfus

DH = mol x DHvap

Heat = mass x Dt x Cp, liquid

Heat = mass x Dt x Cp, gas

Heat = mass x Dt x Cp, solid

+Definitions

Temperature is a measure of the average kinetic energy of the particles in a sample of matter.

A joule is the SI unit of heat as well as all other forms of energy.

Heat can be thought of as the energy transferred between sample of matter because of a difference in their temperatures.

+ Units for Measuring Heat

2

2

1s

mkgmNJ

The Joule is the SI system unit for measuring heat:

The calorie is the heat required to raise the temperature of 1 gram of water by 1 Celsius degree

1 4.18calorie Joules

+ Latent Heat of Phase Change

Molar Heat of Fusion

The energy that must be absorbed in order to convert one mole of solid to liquid at its melting point.

The energy that must be removed in order to convert one mole of liquid to solid at its freezing point.

Molar Heat of Solidification

+ Latent Heat of Phase Change #2

Molar Heat of Vaporization

The energy that must be absorbed in order to convert one mole of liquid to gas at its boiling point.

The energy that must be removed in order to convert one mole of gas to liquid at its condensation point.

Molar Heat of Condensation

+ Latent Heat – Sample Problem

Problem: The molar heat of fusion of water is

6.009 kJ/mol. How much energy is needed to convert 60 grams of ice at 0C to liquid water at 0C?

2 2

2

60 1 6.00920.00

18.02 1

g H O mol H O kJkiloJoules

g H O mol

Massof ice

MolarMass ofwater

Heatof

fusion

+Calculating Energy Changes - Heating Curve for Water

Tem

pera

ture

(o C

)

40

20

0

-20

-40

-60

-80

-100

120

100

80

60

140

Time

DH = mol x DHfus

DH = mol x DHvap

Heat = mass x Dt x Cp, liquid

Heat = mass x Dt x Cp, gas

Heat = mass x Dt x Cp, solid

+

Specific HeatThe amount of heat required to raise the temperature of one gram of substance by one degree Celsius.

+ Calculations involving Specific Heat

cp = ___q__ m x T

q = cp x m x T

cp = Specific Heat

q = Heat lost or gained

T = Temperature change

OR

+

Specific heat of ice = 2.092 J/g°C

Specific heat of water = 4.184 J/g°C

Specific heat of steam = 2.013 J/g°C

Heat of vaporization = 2260 J/g

Heat of fusion = 334 J/g

+Practice Problems

Calculate the energy released if 10 grams of steam at 110℃ is cooled to -20 ℃.

+

Table of Specific Heats

+

A calorimeter is a instrument that measures the energy absorbed or released as heat in a chemical or physical reaction.

+

Specific HeatThe amount of heat required to raise the temperature of one gram of substance by one degree Celsius.

+ Calculations involving Specific Heat

cp = ___q__ m x T

q = cp x m x T

cp = Specific Heat

q = Heat lost or gained

T = Temperature change

OR

+

Table of Specific Heats