Chapter 8 Notes

Types of Chemical Reactions

p.261 - 284

8.1 Chemical Reactions (p.261-269)1. Starting on p.261 at the top, find the definitions for the following:

1. Chemical reaction, Reactant, Product

2. Chemical reactions are written like this: Reactant Product

3. p. 261, write the 4 indications of a chemical reaction (only the italicized section)

4. p.262, write the 3 characteristics of a chemical equation (only the italicized section)

5. p. 263, copy down Table 1 (7 diatomic molecules)

6. What is the difference between a word equation and a formula equation?

7. How does the law of conservation of mass apply to chemical reactions?

8. What does the term yield mean in the context of chemical reactions?

9. p.266, Copy down the following 7 symbols from the chart1. Yields, reversible reaction, (s), (l), (aq), (g), and heated

10.p.269, copy down the italicized portion of number 2.

8.1 section review

Complete questions 1 - 3

8.2 Types of Chemical Reactions

1. Synthesis (or Composition) reactions

2. Decomposition reactions

3. Single-displacement reactions

4. Double-displacement reactionsAcid/Base reactions: Acid + Base salt + water

5. Combustion reactions

1. Synthesis Reactions

aka: composition or addition What happens: two or more substances

combine to form a new compound General Equation: A+X AX Example: Zn + O ZnO

Specific examples – p.278-9 Synthesis Reactions with Oxides

2. Decomposition Reactions

What Happens: a compound is broken down in a reaction which makes two or more simpler compounds

Key words to indicate decomposition: Electrolysis, heated,

General Equation: AXA+X

Example: CaCO3 CaO + CO2 Specific examples – p.280 Metal Carbonates,

Metal Hydroxides, and Metal Chlorates

3. Single-Displacement Reactions

AKA: Single-replacement What happens: one element replaces a

similar element in a compound General equation: AX+B BX + A Example: Zn + 2 HCl ZnCl2 + H2

According to the activity series, only a more reactive metal or nonmetal will replace a cation or anion in a compound.

There are several versions of an activity series, we will use the one on p.286 in your textbook.

Practice p.287 #1-3, then section review #2-3 on your own.

4. Double-Displacement reactions

AKA: double-replacement What Happens: ions from two compounds

change places to produce two new compounds

General Eq: AX + BY AY + BX Ex: HCl + NaOH H2O + NaClFormation of a precipitate p.282Formation of water in acid/base reactions.

5. Combustion Reactions

aka: burning What Happens: reaction of oxygen gas

(O2), which releases heat and light

Production of water p.283 General: CXHY + O2 H2O + CO2

Example: CH4 + 2 O2 CO2 + 2 H2O

How can you tell which type of reaction?

Composition: 2 elements (only 1 product)

Decomposition: 1 reactant (2+ products)

Single-displacement: 1 element and 1 compound

Double-displacement: 2 compounds

Combustion: CXHY and O2

Balancing Chemical Equations (8.1)

What is a Balanced Equation?same number of each type of atom on both sides

of the equation

This equation is NOT balanced:

N2 + H2 NH3

N = 2 N = 1H = 2 H = 3

This equation IS balanced:

N2 + 3 H2 2 NH3

N = 2 N = 2H = 6 H = 6

Steps to balance an equation:

1. Write the chemical reaction:Mg + O2 MgO

2. Count how many of each type of atom are on the reactant side and the product side

Mg + O2 MgO

Mg = 1 Mg = 1

O = 2 O = 1

Steps to balance an equation:

3. Add coefficients to balance the equation Remember, you can only add coefficients, you

can’t change subscripts!

2 Mg + O2 2 MgO

Mg = 1x2= 2 Mg = 1x2= 2

O = 2 O = 1x2= 2

Polyatomic Ions

H2SO4 + Mg MgSO4 + H2

H = 2 H = 2

SO4 = 1 SO4 = 1

Mg = 1 Mg = 1

Note: polyatomic ions are a single item in your inventory – DO NOT separate them into individual elements

Practice

Na + Br2 NaBr

Al(NO3)3 + Li LiNO3 + Al

C3H8 + O2 CO2 + H2O

Summing it up

Practice p.272 (#1ab, 2)Practice p.274 (#1abc)

Predicting Products of Reactions

Step 1: Identify reaction typeStep 2: Label cations and anions on the

reactant side.Step 3: Determine how cations and anions

will recombine on the product side.Step 4: Consult activity series to determine

if reaction will occur.Step 5:Cross charges on any compounds

and determine if anything is diatomic.

Reactants Type of Reaction

Products

CxHy + O2 Combustion Always the same: CO2 + H2O

A + X SynthesisCombine the reactants into one formula: AX

AX Decomposition Break into smaller pieces: A+X

AX + B Single-

Displacement

Is displaced ion positive or negative? Write lone ion plus new compound: A + BX

AX + BY Double-

Displacement

Join positive ion from one compound with negative ion from the second compound, and vice versa: AY + BX

Examples

Ex1: Na + Cl _______

Ex2: H2 + O2

Examples

Ex1: MgBr2 ______ + ______

Ex2: CaCO3 ______ + ______

Examples

Ex1: Li + SrO ______ + ______

Ex2: KOH + Ba ______ + ______

Examples

Ex1: AgNO3 + BeCl2

Ex2: FePO4 + ZnS

Examples

Ex1: C2H6 + O2 CO2 + H2O

Ex2: C6H12O6 + O2

8.2 section review p. 284 (1-4)

Activity Series of the Elements

Section 8.3

Pages 285-287

Activity Series

An activity series organizes elements by how easily they react, or how active they are in a chemical reaction.

Metals: easier loss of electronsNonmetals: easier gain of electrons

ONLY MATTERS IN SINGLE and DOUBLE DISPLACEMENT!

Rules

There is only one rule – an element will replace (or displace) another element only if the second element is below it on the chart.Ex: Lithium is at the top of the chart, so it will

displace any metal in a compound that it is reacting with.

Complete the activity series worksheet (front side only)

Solubility in chemical reactions

How does one know what state of matter a compound is in? How does one know if a precipitate is formed or not?

Use the solubility guidelines chart to determine if a compound is soluble (aqueous, or dissolved in solution) or insoluble (solid, or forms a precipitate)

Complete the worksheet on the back

Homework

Complete both sides of the worksheet titled “Double Displacement Reactions”.

Use your activity series and solubility chart to determine: if a reaction will occur and if any precipitates are formed.

If the reaction will occur, write the products formed. If not, write no reaction.