Chemical Equations and Reactions

By: Erica, Brittany, Dana

There are 5 different types of reactions:◦ Synthesis◦ Decomposition◦ Single replacement◦ Double replacement◦ Combustion

They are used to predict the products of specific reactions

5 Types of Chemical Reactions

Two or more elements or compounds combine to make one compound

• A+B AB Example:

◦ 2Mg+O₂ Combine elements Mg and O to make one compound 2Mg+O₂2MgO

Synthesis

Synthesis◦ C+O₂◦ S₈+8O₂

Practice Synthesis

Synthesis◦ C+O₂CO₂◦ S₈+8O₂8SO₂

Practice Synthesis

A compound is broken down into 2 or more elements or compounds

ABA+B Examples:

◦ 2H₂O◦ Break down the compound 2H₂O◦ 2H₂O2H₂+O₂

Decomposition

Decomposition◦ 2HgO◦ CaCO₃

Practice Decomposition

Decomposition◦ 2HgO2Hg+O₂◦ CaCO₃Ca+CO₂

Practice Decomposition

One part of a compound switches places with an element, forming a new compound

A+BCAC+B Examples:

◦ Fe+CuSO₄◦ Switch compounds Fe and Cu◦ Fe+CuSO₄Cu+FeSO₄

Single Replacement

Single replacement◦ 2Na+2H₂0◦ Mg+2HCl

Practice single replacement

Single replacement◦ 2Na+2H₂02NaOH+H₂◦ Mg+2HClH₂+MgCl₂

Practice single replacement

Parts of 2 compounds switch places to form 2 new compounds

AB+CDAD+CB Examples:

◦ 2KI+Pb(NO₃)₂◦ Elements K and Pb Switch places◦ 2KI+Pb(NO₃)₂2KNO₃+PbI₂

Double Replacement

Double replacement FeS+2HCl HCl+NaOH

Practice Double Replacement

Double replacement FeS+2HClH₂S+FeCl₂ HCl+NaOHNaCl+H₂O

Practice Double Replacement

Any hydrocarbon burned in oxygen to form carbon dioxide and water

Examples of combustion are burning of natural gas, propane, gas, and wood

Example:◦ CH₄+O₂ CO₂+H₂O◦ Methane is burned in oxygen and creates carbon

dioxide and water

Combustion

Combustion 2H₂+O₂ C₃H₈+5O₂

Practice Combustion

Combustion 2H₂+O₂2H₂O C₃H₈+5O₂3CO₂+4H₂O

Practice Combustion

A list of elements used to help predict whether or not a reaction will occur

The elements are organized according to the ease with which the elements undergo certain chemical reactions

In a single replacement reaction, an element can replace any element lower than it on the series

Activity Series

How about Zn + CaCl₂ ?

1. Will this reaction occur?2. Zn + HCl ?

How about Cu+ AgNO3 ?

How about Zn + CaCl₂ ?

1. Will this reaction occur?2. Zn + HCl ?

Yes, Hydrogen is lower than Zinc on the activity series. Therefore, Zinc will combine with Chlorine, and Hydrogen will separate from Zinc.Zn + 2HCl ZnCl₂ + H₂

How about Cu+ AgNO3 ?

How about Zn + CaCl₂ ?

1. Will this reaction occur?2. Zn + HCl ?

Yes, Hydrogen is lower than Zinc on the activity series. Therefore, Zinc will combine with Chlorine, and Hydrogen will separate from Zinc.Zn + 2HCl ZnCl₂ + H₂

How about Cu+ AgNO3 ?

Will not occur

Will occur

Equations should be balanced because the Law of Conservation of Matter states that mass can not be lost or gained in a chemical reaction.

Therefore, the total mass of the reactants must equal total mass of the products

Balancing Equations

Water hydrogen + oxygen H₂O H₂ + O₂

because hydrogen and oxygen exist as diatomic molecules

There are two H molecules and one O molecule in the reactants

There are two H molecules and two O molecules in the products

This is not balanced

Balancing Decomposition of H₂O

H₂O H₂ + O₂ 2 H₂O H₂ + O₂ Now there are more H molecules on the

reactant side 2 H₂O 2 H₂ + O₂ Now there are 4 H molecules on each side

and 2 O molecules on each side Now it’s balanced!

Balancing Decomposition of H₂O

methane + oxygen carbon dioxide + water

CH₄+ O₂ CO₂+ H₂O CH₄+ 2 O₂ CO₂+ 2 H₂O

Try this! Zinc + hydrochloric acid zinc chloride + hydrogen Zn + HCl ZnCl₂ + H₂ Zn + 2 HCl ZnCl₂ + H₂

Writing and Balancing Practice

Try this! Iron sulfide + hydrochloric acid Yield Hydrogen sulfide + iron (III) chloride FeS+HCl H₂S + FeCl₂ FeS+2 HCl H₂S + FeCl₂

Writing and Balancing Practice

http://www.jesuitnola.org/upload/clark/refs/solu_act.htm (activity series)

Sources