Types Of Chemical Reactions

Objective

Distinguish between the 5 different types

of reactions

Predict the products of a reaction

Predict the physical states of products

5 Types of Reactions

Composition/Synthesis

Decomposition

Single Replacement

Double Replacement

Combustion

Composition Reactions aka synthesis rxn

When two or more substances react to form a single

product

2 reactants → 1 product

A + X → AX

H2 + O2 →

MgO + CO2 → 2 H2O

MgCO3

Decomposition

Occurs when a compound is broken down into

simpler substances

Single reactant yields two or more products

(1 reactant → 2 products)

forms a common gas as one of the products; CO2,

O2, SO2, H2O

Decomposition Examples

AX → A+ X

HgO →

CaCO3 →

Hg + O2

CaO + CO2

Single Replacement

One substance replaces another

A metal replaces a metal, if it is more active

A non-metal replaces a non-metal, if it is more

active

Single Replacement Examples

A and B are metals; X and Y are non-metals

A + BX → AX + B OR Y + BX → BY + X

Mg + Zn(NO3)2 →

Cl2 + KBr →

Mg (NO3)2 + Zn

KCl + Br2

Double Replacement

An exchange of partners

The metal replaces the metal and the non-metal

replaces the non-metal

AX + BY → AY + BX

Na2S + Cd(NO3)2 →

BaCl2 + K2CO3 →

NaNO3 + CdS

BaCO3 + KCl

Composition

Two elements or compounds combine to form a

single substance

A + X →

Fe + O2 →

H2O + SO3 →

AX

FeO

H2 SO4

5 Kinds of Decomposition Reactions

Metallic Carbonates

Metallic Hydroxides

Metallic Chlorates

Oxy Acids

Oxides

Metallic Carbonates

CaCO3 →

Metal oxide and carbon dioxide formed

CaO + CO2

Metallic Hydroxides

Many metallic hydroxides (OH-), when heated,

decompose into metallic oxides and water.

Ca(OH)2 →

Metal oxide and water formed

Exceptions to the rule: NaOH and KOH

CaO + H20

Metallic Chlorates

(ClO3-), when heated, decompose into

metallic chlorides and oxygen

2KClO3 →

metal chloride and oxygen formed

2KCl + 3O2

Oxy Acids

Some oxy acids, when heated, decompose

into nonmetallic oxides and water Seltzer Water

H2CO3 →

Acid Rain H2SO3 →

CO2 + H2O

SO2 + H2O

Oxides

Some oxides, when heated, decompose.

2HgO →

2Pb O2 →

2Hg + O2

2PbO + O2

4 Kinds of Single Replacement Reactions

Metal w/ more active metal

Hydrogen in acids w/ more active metal

Hydrogen in water w/ by most active metals

Halogen w/ more active halogen

Metal w/ more active Metal

Replacement of a metal in a compound by a

more active metal (PCS Mazintl)

Zn + CuSO4 →

Zinc replaces the copper, therefore zinc is

more active

ZnSO4 + Cu (s)

Hydrogen in acids w/ more active metals

Replacement of hydrogen, in acids, by metals

more active than hydrogen (PCS Mazintl)

Zn + H2SO4 →

The corresponding metallic compound and

hydrogen gas are formed

Zn SO4 + H2 (g)

Hydrogen in water w/ most active metals

Replacement of hydrogen, in water, by the

most active metals. Which Metals?

All Group I and some of Group II

Ca + 2 H2O →

A hydroxide and hydrogen gas are formed

Ca(OH)2 + H2 (g)

Halogen w/ more active halogen Replacement of a halogen by a more active halogen

Cl2 + 2 KBr →

Br2 + 2 KI →

MgBr2 + I2 →

The corresponding metallic compound and elemental halogen

are formed

2 KCl + Br2

2 KBr + I2

no reaction because Br is more active than I, so I will not replace Br

Activity Series of the elements

A + BX → AX + B

If A replaces B, then A is more active than B

If an element is above another element on the chart, then

it is more active, and will replace the lower positioned

element

All metals above hydrogen displace hydrogen from

hydrochloric acid or dilute sulfuric acid.

P.C.S. Mazintl Activity of HalogensP potassium FluorineC calcium ChlorineS sodium BromineM magnesium Iodinea aluminumz zinci ironn nickelt tinl leadHYDROGENCopperMercurySilver

More Active

Example

Zn (s) + CuSO4 (aq)→

P.C.S. Mazintl Activity of HalogensP potassium FluorineC calcium ChlorineS sodium BromineM magnesium Iodinea aluminumz zinci ironn nickelt tinl leadHYDROGENCopperMercurySilver

More Active

Example

Zn (s) + CuSO4 (aq)→

Mg (s) + Zn(NO3)2 (aq) →

ZnSO4 (aq) + Cu (s)

Mg (NO3)2 (aq) + Zn (s)

Double Replacement AX + BY → AY + BX

usually takes place in a solution of water…all reactant solutions are aqueous

2 compounds → 2 different compounds

1 of these will not be soluble in water…solid (s)

The soluble (dissolved) compound is aqueous…(aq)

In order for you to know if the reaction has occurred, a solid or gas must form

1 product will typically be:

solid: precipitate

gas: CO2 SO2 NH3

Solubility Rules for Double Dis(RE)placement Reactions How to determine which product is the

precipitate

Na+

K+

NH4+

NO3-

[ Will always be soluble in water.

Tells you what won’t precipitate, so assume the other one will

Examples

CaCO3 + 2 HCl →

Pb(NO3)2 + KI →

NaOH + KI → →

CaCl2 + H2CO3

H2O + CO2

PbI2 + 2 KNO3

NaI + KOHno reaction because

both products are

soluble

Combustion

An element or compound reacts with oxygen

Usually produces heat → Exothermic

Combustion of a hydrocarbon always produces carbon

dioxide and water

2 Mg + O2 →

2 CH3OH + 3 O2 →2 MgO + heat

2 CO2 + 4 H20 + heat

Writing Molecular, Complete Ionic, and Net Ionic Equations Molecular Equations: an equation

showing the complete neutral formulas for every compound in the reaction.

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

Complete Ionic Equations: equations that show reactants and products as they are actually present in solution.

Ionic compounds dissociate (dissolve) in water, so they are written as individual ions…if the compound is soluble…check your solubility rules

Complete Ionic Equation of : AgNO3 (aq) + NaCl (aq)→ AgCl(s) + NaNO3 (aq)

Spectator Ions: ions in solution that appear unchanged on both sides of the equation

Net Ionic Equation: equations which show only the species that actually participate in the reactionSpectator ions are omitted from the net ionic

equation

Write the Net Ionic Equation for:

Ag+ (aq) + NO3- (aq) + Na+ (aq) + Cl- (aq) → AgCl(s) + Na+ (aq) + NO3

-(aq)

Write the molecular, complete ionic and net ionic equations for the following:

lead (II) nitrate reacts with lithium chloride.

Write the molecular, complete ionic and net ionic equations for the following:Hydrobromic acid reacts with calcium hydroxide

END