Chemical Reactions

Chemical Reactions Objectives1.Classify and name compounds in chemical reactions2.Describe chemical reactions in word and chemical

equations.3.Balance chemical equations based on the Law of

Conservation of Mass.4.Identify and classify types of chemical reactions

and energy changes involved.5.Predict products and energy changes in a chemical

reaction. 6.Identify and test factors that affect the rate of

chemical reactions.

Chemical Reactions

What is a chemical reaction? • Use your background knowledge to explain

what a chemical reaction is.• Think about chemical changes you have

observed in your surroundings.• Think about chemical changes on an atomic

level.

Chemical Reactions• Substances chemically interact to form different

substances. • A substance can be an element or a compound.

• Chemical bonds are broken and created.

Example: Iron chemically reacts with Oxygen to produce Iron(II) Oxide

Chemical Equations Fe + O2 ------> FeO

Reactants:

• Starting substances.• Chemically interact with one another.• Usually located to the left of the arrow.Products:• Ending substances.• Substances formed from the chemical reaction.• Usually located to the right of the arrow.

Chemical Equations

Fe(s) + O2 (g) ------> FeO (s)

• (s)= substance in solid state• (g)= substancein gaseous state• (l)= substance in liquid state• (aq)= substance dissovled in water.(aqueous solution)

Chemical Reactions Fe(s) + O2 (g) ------> FeO (s)

• Are atoms destroyed or created during a chemical reaction?

• No, they are just rearranged to produce new substances.

Law of Conservation Of Mass

• Matter is not created or destroyed.

• Matter is just rearranged.(mass of reactants = mass of products)

That is why it is important to balance chemical equations.

Conservation of Mass Lab

• Observe the conservation of mass lab, to understand why it is important to balance chemical equations.

Balancing Chemical Equations 2Fe(s) + O2 (g) ------> 2FeO (s)

Balancing Chemical Equations:1. Add coefficients in front of substances, do

NOT change subscripts.

2. First balance elements that only appear once on each side of the equation.

Balancing Chemical Equations

Chemical Reactions Bell Ringer1. N2 (g) + H2(g) --------> NH3(g)

a. What is the chemical name of one of the reactants?

b. What is the chemical name of the product?

c. What state of matter is all the substances in this reaction?

d. Balance the chemical equation if needed.

Type of Anion

Name of Acid

Monatomic anion (-ide ending)

hydro + stem + ic

Polyatomic anion(-ite ending)

stem + ous

Polyatomic anion(-ate ending)

stem + ic

Balancing Chemical Equations

Types of Chemical Reactions

1. Synthesis (A+ B ----> AB)2. Decomposition (AB------> A + B)3. Single Replacement (A+ BC ---> B + AC)4. Double Replacement (AB + CD ---> CB + AD)5. Combustion (CxHx + O2 ----> CO2 + H2O)

6. Neutralization (Acid + Base--> H2O + Salt)

Chemical Reactions Objectives1. Identify and classify types of chemical reactions.

2. Identify energy changes involved with chemical reactions.

3. Predict products and energy changes in a chemical reaction.

Synthesis (Combination) Reaction

• 2 or more substances chemically combine to form a single substance.

• A + B ---> AB + energy

• Energy released into surroundings is more than energy absorbed by the system.

( Energy of surroundings > Energy of system)

Decomposition Reaction

• A compound breaks down into simpler substances.

• AB + energy ----> A + B

• Energy of system > Energy of surroundingsWhy?

Single Replacement Reaction

• An element replaces another element in a compound.

• A + BC --------> B + AC + energy

• Energy of surroundings > Energy of system

Double Replacement Reaction

• Exchange of cations between two compounds. • AB + CD + energy ----> CB + AD + more energy

• Energy of Surrounding > Energy of System

Combustion Reaction

• Fuel (hydrocarbons) reacts with oxygen to produce predictable substances and energy.

• CxHx + O2 ----> CO2 + H2O + ENERGY

• Energy of Surroundings > Energy of System

Neutralization • Acid and Base react to produce predictable

products. • Changes the pH to 7 (neutral).

Acid + Base -------> H2O + Salt

Salt: An ionic compound. The cation comes from the base and the anion from

the acid.

Class Reminders:

• Acid Rain Article (15pts.)

• Balance Chemical Equations Worksheet (10pts.) (balance and classify equations)

• Word Equation Worksheet (10pts.)

*3rd Quarter Ends: March 8th*

Chemical Reaction Lab

Purpose: • Perform and observe types of chemical

reactions.• Determine reactants and predict products.• Classify chemical reactions.• Balance chemical reactions.• Write a formal lab report

Chemical Equations to LabReaction Chemical Equation

1

2

3

4

5

6

7

8

Types of Chemical Reactions

1. Synthesis (A+ B ----> AB)2. Decomposition (AB------> A + B)3. Single Replacement (A+ BC ---> B + AC)4. Double Replacement (AB + CD ---> CB + AD)5. Combustion (CxHx + O2 ----> CO2 + H2O)

6. Neutralization (Acid + Base--> H2O + Salt)

Chemical Equations to Lab

Just need to check and see if they are balanced. 1. Mg + O2 ------>

2. Mg + HCl ----> 3. (NH4)2(CO3) -----> NH3 + CO2 + H2O

4. Ca(CO3) + HCl ----> CaCl2 + H2O + CO2

5. Zn + CuCl2 ---->

6. CuCl2 + Na3(PO4) --->

7. HCl + Na(OH) ----> H2O + NaCl

8. C2H6O + O2 ----->

Chemical Reaction Review1. What are the coefficients that will balance the

chemical equation below? AlCl3 + Na(OH) ----> Al(OH)3 + NaCl

a. 1,3,1,3b. 3,1,3,1c. 1,1,1,3d. 1,3,3,12. What type of chemical reaction is in question 1?

3. Predict the product and balance if needed: Ba (s) + O2 (g) ---------->

Balancing and Classifying Chemical Reactions

Chemical Equations to Lab

Just need to check and see if they are balanced. 1. Mg + O2 ------> MgO

2. Mg + HCl ----> MgCl + H2

3. (NH4)2(CO3) -----> NH3 + CO2 + H2O

4. Ca(CO3) + HCl ----> CaCl2 + H2O + CO2

5. Zn + CuCl2 ----> ZnCl2 + Cu

6. CuCl2 + Na3(PO4) ---> Cu3(PO4)2 + NaCl

7. HCl + Na(OH) ----> H2O + NaCl

8. C2H6O + O2 -----> CO2 + H2O

ConclusionNeeds to include the following:• Identify and explain the types of reactions obsvd. ?

• Which reaction(s) did you like the best and why?

• Based on data section explain which reactions were exothermic and endothermic.

• What did you learn from this lab?

Predicting Products in a Chemical Reaction

a. Ca + N2 --------> ?

b. Cu2S -------> ?

c. NaBr + F2 ------> ?

d.CH4 + O2 ----->

Balancing and Classifying Equations Quiz Types of Chemical Reactions 1. Synthesis 2. Decomposition 3. Single Replacement 4. Double Replacement 5. Combustion 6. Neutralization

Predicting Products• Check my webpage for correct chemical formulasprior to balancing.

Predicting Single Replacement Reactions• An Activity Series can help us predict if a single

replacement reaction will take place.

Activity Series Lab Hypothesis CuCl2(aq) Ag(NO3) HCl (aq) dH(OH) (l)

Copper (s)

Magnesium (s)

Zinc (s)

Calcium (s)

Activity Series Lab

• Complete conclusion

• Complete Post Lab Questions

Activity Series Lab1. Using the Activity Series Table, predict whether

the following single replacement reactions would occur:

a. Li + MgCl

b. Hg + Na3P

c. Pb + HF

Predicting Single Replacement Reactions• An Activity Series can help us predict if a single

replacement reaction will take place.

Activity Series Lab

• Complete conclusion

• Complete Post Lab Questions

Chemical Reaction Study Guide Changes

1. Vocabulary words: Thermochemistry10. HgO + energy ------> Hg + O211. Fe + F2 ----------> FeF3 + energy

12. CH4 + O2 ---------> CO2 + H2O + energy

15. K(OH) + H3(PO4) ------->

18. Omit last word equation.

Chemical Reaction Review1. What are the coefficients that will balance the

chemical equation below? AlCl3 + Na(OH) ----> Al(OH)3 + NaCl

a. 1,3,1,3b. 3,1,3,1c. 1,1,1,3d. 1,3,3,12. What type of chemical reaction is in question 1?

3. Predict the product and balance if needed: BaS + Mg ---------->

ThermochemistryEnergy changes that occur within reactions.

Endothermic Reactions Exothermic Reactions

Exothermic Reaction

• Energy absorbed < Energy released. • The chemical reaction becomes cooler and its

surroundings gets warmer. • Energy is on the product side.

• C8H18 + O2 -------> CO2 + H2O + energy

Endothermic Reactions• Energy absorbed > Energy released• Chemical reaction gets warmer and its

surroundings gets cooler. • Energy is on the reactant side.Ex. Photosynthesis

Chemical Reaction Energy Diagram

Chemical Reaction Energy Diagram• Activation Energy (Ea): The amount of kinetic energy needed to be absorbed from the surroundings for thechemical reaction to occur.

H : The amount of kinetic energy released into the into the surroundings.

Chemical Reaction Energy DiagramExothermic Reaction

Chemical Reaction Energy DiagramEndothermic Reaction

Activation Energy

Chemical Reactions Objectives1.Classify and name compounds in chemical reactions2.Describe chemical reactions in word and chemical

equations.3.Balance chemical equations based on the Law of

Conservation of Mass.4.Identify and classify types of chemical reactions and

energy changes involved.5.Predict products and energy changes in a chemical

reaction. 6.Identify and test factors that affect the rate of

chemical reactions. (Chpt. 18.1)

Chemical Reaction Rates

Assignment:Read Section: 18.1 in textbook (pg. 540)

Chemical Reactions Rates• Reaction Rates = how fast the reactants

chemically change into the products. • Collision Theory: Reactant particles will react to

form products when they collide and exchange enough kinetic energy with one another.

Rates of Chemical Reactions

• What are factors that can affect the rates of reactions?

Rates of Chemical Reactions

• What are factors that can affect the rates of reactions?

• Temperature• Concentration of Reactants• Surface Area of Reactants• Catalysts• Inhibitors

Temperature of Reaction

What if we increase the temperature of a reaction?

What if we decrease the temperature of a reaction?

Concentration

• Increase concentration of reactants?

• Decrease concentration of reactants?

Surface Area

• Increase surface area of reactants?

• Decrease surface area of reactants?

Catalysts

• Catalysts speed up reactions, but they are not apart of the chemical reaction.

Ex. Enzymes keep your body temperature around 37oC (98 oF) by speeding up important biological reactions.

Catalyst and Energy Change

Inhibitors

• Inhibitors slow down a chemical reaction.• Inhibitors bind to a catalyst and prevent it

from speeding up a reaction. Ex. Preservation of food. Antioxidants prevent

foods from becoming stale or moldy.

Soln. A Concentration vs. Avg. Reaction Times

TimeConc

G1 G2 G3 G4 G5 G6 G7 Avg.

A1 7 6 9 9.4 5 3 4.0

A2 6.4 9 9.76 9.5 8 9 15.2

A3 4.8 12 9.4 13.4 12 6 22.6

A4 8.9 15 15.0 19.1 19.1 14 24.3

Activation Energy• Activation energy = minimum energy

colliding reactants must have for a reaction to occur. (Energy hump.)

Catalyst and Energy Change