Types of Chemical Reactions

Synthesis (S):

Decomposition (D):

Single Replacement (SR):

Double Replacement (DR):

Combustion (C):

Will it react?

Types of Chemical Reactions

Learning Target 4.3.1 : I can classify types of chemical reactions based on patterns in reactants/products of a written equation as synthesis, decomposition, single replacement, double replacement, or combustion.

All reactions occur according to several different patterns. Take note of each pattern below and use it to identify reaction types.

Synthesis (S): 

Synthesis reactions are sometimes called Combination reactions because

Two or more substances react to form a single compound.

Forms: 

Element + Element → Compound

A + B → AB

Examples:

2Mg + O2 → 2MgO

S8 + 8O2 → 8SO2

^[1]Cartoon: Skinny bird will eat the fat, juicy worm (reactants) to produce one full bird (product).

Decomposition (D):

A compound is broken down into small, simpler parts.

Forms:

Compound → Element + Element (smaller parts)

AB → A + B

Examples:

2HgO → 2Hg + O2

2NaCl → 2Na + Cl2

^[2]Cartoon: You start with a baby turtle in a shell (reactant) that produce a baby turtle plus it’s shell (products) as two separate products.

Single Replacement (SR):

A free element switches places with an element of the compound.

NOTE: Look at the activity series to see if reaction takes place.

Forms:

Element + Compound → Element + Compound

A + BC → B + AC

D + AE → E + AD

Examples:

2Na + 2H2O → H2 + 2NaOH

Cl2 +2NaI → I2 + NaCl

^[3]Cartoon: Single guy (element) on the left ‘cuts in’ to dance with an already partnered couple (compound) that results in a new couple (compound) and different single guy (element) as products.

The Activity Series

Depending on how reactive a lone element is in the reactants of a single replacement reaction, the reaction may not occur. Watch this video^[4] for an explanation of how the activity series determines whether or not a reaction will occur.

Here is a (printable) copy of the activity series^[5] for you to utilize when writing written chemical equations.

Double Replacement (DR): 

An exchange of positive ions between two compounds.

NOTE: Look at the Solubility Rules to determine product precipitates (if a reaction will occur).

Forms:

Compound + Compound → Compound + Compound

AB + CD → AD + CB

Examples:

Pb(NO3)2 + 2KI → PbI2 + 2KNO3

CaCl2 + MgO → CaO + MgCl2

^[6]Cartoon: Each man has a hat (compound + compound). Each man trades hats during chemical reaction. In the products, each man has a new hat (new compound + compound).

To determine if a Double Replacement will occur and what the precipitate will be, refer to these Solubility Rules^[7]. This Solubility Chart^[8] references the same rules, just in another format.

Combustion (C): 

A hydrocarbon (compound that contains C and H) reacts with oxygen often producing energy in the form of heat and light.

Forms: Very specific!

Hydrocarbon + oxygen → carbon dioxide + water

CxHx + O2 → CO2 + H2O

Example:

CH4 + 2O2 → CO2 + 2H2O + heat + light

^[9]This image shows how the molecules in the combustion of methane rearrange. The red squiggly arrow represents heat as a product.

Goal 4.3.1a: I can classify the following reactions as Synthesis, Decomposition, Single Replacement, Double Replacement, or Combustion based on the patterns of the reactants/products.

Practice classifying and balancing chemical reactions in this practice sheet^[10].

Check your answers with this KEY^[11].

Also check out Mr. Carmen’s blog practice quiz^[12].

Will it react?

Learning Target 4.3.2 : I can use solubility and activity series to determine whether a double replacement or a single replacement will occur.

Goal 4.3.2a: I can predict whether a Single Replacement or Double Replacement reaction will occur based on The Activity Series and Solubility Rules.

How do we know if a reaction will take place?

To predict if a single displacement reaction will occur, you will need The Activity Series.^[13] A metal higher in the list will replace any metal or hydrogen below it.

To predict if a double displacement reaction will occur, you will need Solubility Rules^[14]. There must be some reason for the exchange to occur. If a precipitate, gas or water is produced the reaction will proceed. To determine if there is a precipitate, look for those products that are insoluble (i) in the Solubility Rules chart.

Complete this Practice Sheet^[15] (4.3.2 worksheet) to determine if the Single Replacement or Double Displacement reactions will react. You will also get to predict the products and balance the equations.

How did you do? Check the KEY^[16] to the Practice Sheet.

This Reactions Lab will allow you to practice everything you have learned in this lesson.