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Chemical Reactions

Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products Separates reactants from products (s)Solid

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Page 1: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Chemical Reactions

Page 2: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Symbols used in writing reaction equations

+ Separates two or more reactants or

products

Separates reactants from products

(s) Solid state

(l) Liquid state

(g) Gaseous state

(aq) Water solution

Page 3: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

A chemical reaction always has a change in energy

eitherHeat is given off - Exothermic

orHeat is used - Endothermic

Page 4: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

• Breaking bonds (overcoming forces of attraction) requires energy, so you have to add heat endothermic

• Making bonds gives off energy exothermic

• Most chemical reactions are exothermic (happens naturally)

Page 5: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Types of Reactions

1. Combustion reactions2. Synthesis reactions3. Decomposition reactions4. Single replacement reactions5. Double replacement reactions

• You will need to be able to identify the type of reaction and predict the product(s)

Page 6: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Steps to Writing Reaction Equations

1. Identify the type of reaction2. Predict the product(s) using the type of

reaction as a model3. Balance it! (Law of Conservation of Mass)4. ***Don’t forget about the diatomic elements!

(BrINClHOF) Note: In a compound, it can’t be a diatomic element

because it’s not an element anymore, it’s a compound!

Page 7: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Combustion Reactions

Combustion reactions occur when a hydrocarbon (a compound containing carbon and hydrogen) reacts with oxygen gas.

Page 8: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Combustion Reactions

In general: CxHy + O2 CO2 + H2O

Products are ALWAYS CO2 and H2O.

Page 9: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Combustion

• Example C5H12 + O2 CO2 + H2O

Write the products and balance the following combustion reaction:

C10H22 + O2

Page 10: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

1. Synthesis reactions• Synthesis reactions occur when two substances

(generally elements) combine and form a compound.

• element + element 1 compound• Basically: A + B AB

• Example: 2H2 + O2 2H2O

• Example: C + O2 CO2

Page 11: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Synthesis Reactions

• Here is another example of a synthesis reaction

Page 12: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

For ionic compounds (metal + non-metal) remember to use the elements’ electrical charges when writing the formula

For example:

Al + O2 Al2O3

Page 13: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

PracticePredict the products. Write and balance the following

synthesis reaction equations:

• Sodium metal reacts with chlorine gas • Solid Magnesium reacts with fluorine gas • Aluminum metal reacts with fluorine gas

Page 14: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

2. Decomposition Reactions• Decomposition reactions occur when a

compound breaks up into the elements or in a few to simpler compounds

• The opposite of synthesis reactions• 1 Compound Element + Element • In general: AB A + B• Example: 2 H2O 2H2 + O2

Page 15: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Decomposition Reactions

• Another view of a decomposition reaction:

Page 16: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Practice

Predict the products. Then, write and balance the following decomposition reaction equations:

• Solid Lead (IV) oxide decomposes

• Aluminum nitride decomposes

Page 17: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Practice

Identify the type of reaction for each of the following synthesis or decomposition reactions, and write the balanced equation:

N2(g) + O2(g)

Co(s)+ S(s)

NI3(s)

Page 18: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

3. Single Replacement Reactions• Single Replacement Reactions occur when one

element replaces another in a compound.• A metal can replace a metal (+) OR

a nonmetal can replace a nonmetal (-).• element + compound product + product

A + BC AC + B (if A is a metal) ORA + BC BA + C (if A is a nonmetal)

(remember the cation always goes first!)

When H2O splits into ions, it splits intoH+ and OH- (not H+ and O-2 !!)

Page 19: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Single Replacement Reactions

• Another view:

Page 20: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Single Replacement is also known as oxidation-reduction

The transfer of electrons from metals to nonmetals

Page 21: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

A replacement reaction occurs only if a more reactive element replaces a less reactive element

(Never the other way around)

Page 22: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Single Replacement Reactions

Write and balance the following single replacement reaction equation:

Zinc metal reacts with aqueous hydrogen chloride

Note: Zinc replaces the hydrogen ion in the reaction

Page 23: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Single Replacement ReactionsSodium chloride solid reacts with fluorine gas

Aluminum metal reacts with aqueous copper (II) nitrate

Page 24: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

4. Double Replacement Reactions

• Double Replacement reactions involve an exchange of ions between two compounds.

• A metal replaces a metal and a nonmetal replaces a nonmetal in a compound

• Compound + compound product + product

• AB + CD AD + CB

Page 25: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Double Replacement Reactions

• Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together

• Example: AgNO3(aq) + NaCl(s) AgCl(s) + NaNO3(aq)

• Another example:K2SO4(aq) + Ba(NO3)2(aq) KNO3(aq) + BaSO4(s)

Remember! Cations are always written first!!

Page 26: Chemical Reactions. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid

Practice

Predict the products. Balance the equation HCl + AgNO3

CaCl2 + Na3PO4

KOH + CuSO4