Chemical Reactions January 9th and 10th

Chemical Reactions Bell ringerBelow are two examples of chemical reactions.

Answer the following questions about the below reactions.

1) Label the following parts: Reactants Products yields Coefficient subscript

2) Make a list of 3 things that the below reactions have in common.

3) Make a list of 3 things that are different about the below reactions.

Mg + O2 → 2 MgO ZnS → Zn + S

The basic parts of a chemical reaction

Comparing reactions:

Mg + O2 → 2 MgO ZnS → Zn + S

Types of Reactions

5 types of chemical reactions: 1. Synthesis reactions2. Decomposition reactions3. Single displacement reactions4. Double displacement reactions

A. Acid Base reactionsB. Oxidation reduction reactions

5. Combustion reactions

Writing Reactions Identify the type of reaction. Predict the product(s) based on the type of

reaction. Balance it:

Law of conservation of matter: matter cannot be created or destroyed only transferred.

Don’t forget about the diatomic elements! (gens) Oxygen is O2 as an element.

In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

Balancing Reactions

• All reactions must have same # of elements on each side of reaction…

• See data table provided.

Synthesis and Decomposition

Monday January 14th and 15th

Synthesis reactions- Combination• two substances (generally elements)

combine and form a compound.

• reactant + reactant 1 product• A + B AB• Example: 2H2 + O2 2H2O

• Example: C + O2 CO2

Synthesis Reactions

• Here is another example of a synthesis reaction

Practice

• Predict the products. • Na(s) + Cl2(g)

• Mg(s) + F2(g)

• Al(s) + F2(g)

Decomposition Reactions• Compound breaks up into the elements or

in a few to simpler compounds• Reactant Product + Product • AB A + B

• Example: 2 H2O 2H2 + O2

• Example: 2 HgO 2Hg + O2

Types: Decomposition

Example 2HgO → 2Hg + O2

O Hg

O Hg

Hg

O O Hg

+

General: AB A + B

Practice

• Predict the products. Then, write and balance the following decomposition reaction equations:

• Solid Lead (IV) oxide decomposes PbO2(s)

• Aluminum nitride decomposes AlN(s)

Homework:

• Decomposition Pre-lab

• When finished get pre-lab checked and approved.

Replacement Reactions

Wednesday January 16th and Thursday January 17th

Single Replacement Reactions• one element replaces another in a compound.• A metal replaces a metal (+) OR

a nonmetal replaces a nonmetal (-).• element + compound compound + element

A + BC AC + B (if A is a metal) ORA + BC BA + C (if A is a nonmetal)

(remember the cation always goes first!)

When H2O splits into ions, it splits intoH+ and OH- (not H+ and O-2 !!)

Single Replacement Reaction Example

• Zinc metal reacts with aqueous hydrochloric acid

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

Note: Zinc replaces the hydrogen ion in the reaction

2

Single displacement Example

CuCl2 + Zn → ZnCl2 + Cu

ZnClCl Cu +

AB + C CB + A

ClCl Zn Cu+

Single Replacement Reactions• Sodium chloride solid reacts with fluorine gas NaCl(s) + F2(g) NaF(s) + Cl2(g)

Note that fluorine replaces chlorine in the compound

• Aluminum metal reacts with aqueous copper (II) nitrate

Solve the products for the below reaction: Al(s)+ Cu(NO3)2(aq)

2 2

Double Replacement Reactions

• Metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound. (Must be in solution)

• Compound + compound compound + compound

• AB + CD AD + CB

Double displacement Example

MgO + CaS→ MgS + CaO

General: AB + CD AD + CB

SOMg Ca+

O S

Mg Ca+

Double Replacement Reactions

• More examples:

AgNO3(aq) + NaCl(s) AgCl(s) + NaNO3(aq)

K2SO4(aq) + Ba(NO3)2(aq) KNO3(aq) + BaSO4(s)

2

Practice

• Predict the products. Balance the equation1. CaCl2(aq) + Na3PO4(aq)

2. Pb(NO3)2(aq) + BaCl2(aq)

3. FeCl3(aq) + NaOH(aq)

4. KOH(aq) + CuSO4(aq)

Homework

• Replacement Pre-lab

• When finished get approved

Replacement Reactions Lab

Tuesday January 22nd and Wednesday January 23rd

Lab Safety

• Follow only directions give in your lab book.

• Safety goggles must be worn at all times. • Area must be completely cleaned up when

finished…. • Once finished, you will copy down the

notes that you find on the overhead.

Combustion Reactions• hydrocarbon reacts with

oxygen gas.• called burning!!!

• In order to burn something you need the 3 things in the “fire triangle”:1) A Fuel (hydrocarbon)2) Oxygen 3) Something to ignite the reaction (spark)

Combustion Reactions• In general:

CxHy + O2 CO2 + H2O

• Products in combustion are ALWAYS carbon dioxide and water.

• Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C8H18)

Combustion• Example

• C5H12 + O2 CO2 + H2O

• Write the products and balance the following combustion reaction:• C10H22 + O2

5 68

Homework

• Finish your chemical reactions worksheet.

• Find all the reactions that are combustion reactions and label them… Then, balance them like shown in class.

STOP

• This is the end of notes for types of chemical reactions…