CHEMICAL REACTIONS

The process by which one or more substances are changed into one or more different substances

Equations

Reactions are represented by a chemical equation

Reactants Products

Must have the same number and type of atoms on

both sides of the equation

Synthesis Reactions

Two reactants produce one product Examples:

NH3 + HCl NH4Cl

H2 + O2 H2O

Ag + S Ag2S

Al + Cl2 AlCl3

Decomposition

One reactant produces two products Examples

Ag2O Ag + O2

PCl5 PCl3 + Cl2

H2O2 H2O + O2

CuO Cu + O2

Single Displacement

One element and one compound producing a different element and compound

Examples

Fe + H3(PO4) H2 + Fe3(PO4)2

H2 + CuO Cu + H2O

Zn + HCl H2 + ZnCl2

Cl2 + KBr Br2 + KCl

Double Displacement

Two compounds producing two different compounds

Examples:

Al(NO3)3 + NaOH Al(OH)3 + NaNO3

PbCl2 + Li2SO4 PbSO4 + LiCl

ZnBr2 + AgNO3 Zn(NO3)2 + AgBr

BaCl2 + KIO3 Ba(IO3)2 + KCl

Combustion

A hydrocarbon reacts with oxygen to produce

carbon dioxide and water

Examples:

CH4 + O2 CO2 + H2O

C6H12O6 + O2 CO2 + H2O

Using words…

Chemical Equations from Names

magnesium and hydrogen chloride produce hydrogen and magnesium chloride

calcium hydroxide and lithium chloride produce lithium hydroxide and calcium chloride

decompose copper (II) oxide into copper and oxygen

aluminum and iron (III) oxide produce iron and aluminum oxide

combustion of butane (C4H10) in air to produce carbon dioxide and water

Predicting the Product

Predicting the Product - Rules

1. If hydrocarbon reacts with oxygen combustion

reaction

i. The products will be CO2 and H2O.

2. If two elements or very simple molecules combine

synthesis reaction.

i. The products will be predictable using the rules of

ionic bonding.

Predicting the Product – More Rules

3. If starting with one compound decomposition

reaction.

i. The products will be very simple molecules, or some

elements, or both.

a. Remember the rules for metals and non-metals

4. If a pure element reacts with another compound

(usually ionic) single displacement reaction.

i. The pure element (cation) switches places with

another element (cation) in the other compound.

Predicting the Product – More Rules

5. If two ionic compounds combine double

displacement reaction.

i. Switch the cations and balance out the charges to

figure out what will be made.

Predict the Product - Practice

Magnesium and nitrogen

Copper II oxide is decomposed into its elements

Chlorine and potassium bromide

Calcium hydroxide and hydrogen sulfate

Iron (III) chloride and sodium hydroxide

Methane is combusted in air

Solubility and Precipitates

Precipitate

Precipitation is the formation of a solid in a solution

or inside another solid during a chemical reaction

the solid formed is called the precipitate

SOLUBILITY RULES

All common salts of Group I elements and

ammonium are soluble

All common acetates and nitrates are soluble

All binary compounds of Group 7 (other than F)

with metals are soluble except those of silver,

mercury I and lead

More Solubility Rules

All sulfates are soluble except those of barium,

strontium, calcium, silver, mercury I and lead

Except for those in Rule 1, carbonates, hydroxides,

oxides, sulfides and phosphates are insoluble

Precipitate Reaction

General form: AB(aq) + CD(aq) → CB(s) + AD(aq)

Description: In a precipitation reaction two solutions

are mixed together to produce an insoluble solid

which is called the precipitate.

This type of reaction is also called a double

displacement reaction

A little more on Chemical Reactions

Physical States of Matter and Symbols

All physical states are given at standard

temperature and pressure for each chemical

species.

(aq) = aqueous solution (dissolved in water, from aqua

or water).

(l) = liquid

(s) = insoluble solid or precipitate.

(g) = gas

Precipitate Reactions

General form: AB(aq) + CD(aq) → CB(s) + AD(aq)

Is a double displacement reaction!!

Examples

Lead nitrate(aq) + Potassium iodide(aq) → Lead iodide(s) + potassium nitrate(aq)

Pb(NO3)2(aq) + 2KI(aq) → PbI2(s) + KNO3(aq)

Silver nitrate(aq) + sodium chloride(aq) →Silver chloride(s) + sodium nirate(aq)

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

Mercury(II) nitrate(aq) + Potassium iodide(aq) → Mercury iodide(s) + Potassium nitrate

Hg(NO3)2(aq) + 2KI(aq) → HgI2(s) + KNO3(aq)

Barium chloride(aq) + Sodium sulfate(aq) → Barium sulfate(s) + Sodium chloride(aq)

BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + NaCl(aq)

Copper sulfate(aq) + Sodium hydroxide(aq) → Copper hydroxide(s) + Sodium sulfate(aq)

CuSO4(aq) + 2NaOH(aq) → Cu(OH)2(s) + Na2SO4(aq)

Net Ionic Equations

What are Net Ionic Equations?

Equations that show only the soluble, strong

electrolytes reacting (ions) and omit the spectator

ions, which go through the reaction unchanged.

Bare bones of the chemical reaction

Usually take place in aqueous environments

Ions separate in water into cations and anions

Net Ionic Equations – in words

1. Write the (balanced!) molecular equation first

Reaction products: swap cations and anion

Predict solubility (using Solubility rules)

Net Ionic Equations – in words

2. Write the complete ionic equation next

(s) compounds don’t ionize

(aq) compounds do ionize

ion subscripts in the molecular equation become

coefficients in the complete ionic equation

Ie (NO3)2 becomes 2(NO3)

Net Ionic Equations – in words

3. Write the net ionic equation next

cancel spectator ions

The net ionic equation is a “simplified” form

of the complete ionic equation

Net Ionic Equations

Balanced Chemical Equation:

Pb(NO3)2(aq) + 2NaI(aq) PbI2(s) + 2NaNO3(aq)

“Complete Ionic” Equation:

Pb2+(aq) + 2NO3

-(aq) + 2Na+

(aq)+ 2I-(aq) PbI2(s) + 2Na+(aq) + 2NO3

- (aq)

Cancel the “spectator ions” that appear on both sides of the arrow

Pb2+(aq) + 2NO3

-(aq) + 2Na+

(aq)+ 2I-(aq) PbI2(s) + 2Na+(aq) + 2NO3

- (aq)

“Net Ionic” Equation:

Pb2+(aq) + 2I-(aq) PbI2(s)