Types of Chemical Reactions

Synthesis, Combustion, Decomposition and Replacement

You can think of atoms as people getting together as couples...

Analogy Chemical Reaction

One person An ion or element

A couple A compound

Switching partners A replacement reaction

The Get Together…

Synthesis

Decomposition

Decomposition

Single Replacement Reactions

Single Replacement Reactions

Double Replacement Reaction

Double Replacement Reaction

Combustion

Combustion

How does this analogy break down?

People in Relationships Chemical Reactions

People can switch partners whenever they want

The ions or elements in a compound “switch partners” according to rules

We usually just think about one partner and one couple

In chemistry, we usually are dealing with billions of particles reacting at once

People don’t assume different states of matter

In double replacement reactions, there will be a change of state (a solid, liquid, or gas is formed)

People aren’t swimming in water

Displacement reactions generally happen in aqueous solutions

Let’s look at the reactions in more detailSynthesis

Decomposition

Single-Replacement

Double-Replacement

Combustion

Combustion

What are some types of combustion you are

familiar with?Every cell in your body is carrying out combustion

Combustion

Oxygen combines with a metal, non-metal, or compound

Creates a metal oxide, non-metal oxide, or 2 or more oxides

Releases energy – heat, light

Can be a slower process too…

Synthesis

2 or more reactants combine to make a product

Decomposition

A compound breaks down into two or more substances

Single Replacement

A metal replaces a hydrogen

A metal replaces another metal

We use an activity series to predict which metals are “stronger” and can knock out other metals from compounds

Activity SeriesThe most active metals are at the top. These will replace metals below them.

The halogens are also listed in order of most active at the top to least active at the bottom.

More active elements replace less active elements in single replacement reactions

Single Replacement Examples

2 AgNO3 + Cu Cu(NO3)2 + 2 Ag

Fe + Cu(NO3)2  Fe(NO3)2 + Cu

Zn + 2HCL ZnCl2 + H2

Double Replacement Reactions

Produces a precipitate, liquid or gas

All four of the ions switch partners

Aqueous solution

Double Replacement Examples

AgNO3(aq) + KCl(aq) AgCl(s) + KNO3(aq)

CaCO3(aq) + 2 HCl(aq) CaCl2(aq) + H2O(l) + CO2(g)

HCl(aq) + NaOH(aq) HOH(l) + NaCl(aq)

How to identify a reaction

Steps to determine type

of reactionWrite the chemical

equation

Determine what is happening in the reaction

Use the table to identify the type of reaction

Check your answer by comparing the chemical equation to the generic equation

Be systematic – it will help you identify the reaction type and the products!

How to identify a reaction

Example: Identifying a reactionCaO (s) + CO2 (g) CaCO3 (s)

2 compounds are reacting to form one compound

This is a synthesis reaction

A + B AB

Example:

Solid calcium oxide and carbon dioxide gas react to produce solid calcium carbonate

Summary

The main types of reactions

Combustion – reaction with oxygen

Synthesis – two compounds or elements getting together

Decomposition – One compound splitting up

Replacement – Another ion moves in

Replacement Reactions: 2 types Single replacement – a

stronger cation steps in and replaces a weaker anion

Double replacement – 2 cations switch places, forming a precipitate, a liquid, or a gas

You try it!

Work on these examples together in pairs. Write the reaction Balance the equation Classify the reaction Be prepared to present your results on the board!

Magnesium and Hydrochloric acid form Magnesium Chloride and Hydrogen

Carbon Dioxide and Water form Carbonic Acid (H2CO3)

Silver Nitrate and Sodium Chloride form Silver Chloride and Sodium Nitrate

Heating sodium bicarbonate (NaHCO3) releases water and carbon dioxide and sodium carbonate

You try it!

Magnesium and Hydrochloric acid form Magnesium Chloride and Hydrogen: Mg + HCl MgCl + H2 (skeleton equation) 2Mg + 2HCl 2MgCl + H2 (balanced equation) Single replacement (reaction type)

Carbon Dioxide and Water form Carbonic Acid (H2CO3): CO2 + H2O H2CO3 (skeleton equation) CO2 + H2O H2CO3 (it’s already balanced!) Synthesis (reaction type)

You try it!

Silver Nitrate and Sodium Chloride form Silver Chloride and Sodium Nitrate AgNO3 + NaCl AgCl + NaNO3 (skeleton equation) AgNO3 + NaCl AgCl + NaNO3 (already balanced) Double replacement (reaction type)

Heating sodium bicarbonate releases water and carbon dioxide and sodium carbonate NaHCO3 Na2CO3 + H2O + CO2 (skeleton equation)

2NaHCO3 Na2CO3 + H2O + CO2 (balanced equation)

Decomposition (reaction type)