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