Chemical Reactions

Types of ReactionsTypes of Reactions• There are six types of chemical

reactions that we learn about in Chemistry:

1. Synthesis or composition reactions2. Decomposition reactions3. Single displacement (a.k.a. replacement)4. Double displacement (a.k.a. replacement)5. Combustion6. Acid-Base

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

Some elements are found bonded to themselves- like Some elements are found bonded to themselves- like identical twins. These are called diatomic molecules.identical twins. These are called diatomic molecules.

The “Diatomic 7” are:The “Diatomic 7” are:Hydrogen, HHydrogen, H22

Nitrogen, NNitrogen, N22

Oxygen, OOxygen, O22

Fluorine, FFluorine, F22

Chlorine, ClChlorine, Cl22

Bromine, BrBromine, Br22

Iodine, IIodine, I22

Things to know:Things to know:

The diatomic 7 make a “7” The diatomic 7 make a “7” starting at element #7, plus Hstarting at element #7, plus H

Follow the ‘rules’ of bonding Follow the ‘rules’ of bonding when writing compounds or when writing compounds or

moleculesmoleculesFor example:For example:

How does Sodium bond with Chlorine?How does Sodium bond with Chlorine?

NaNa+1+1 Cl Cl-1-1 so it will be: NaCl so it will be: NaCl

HH+1+1 will bond with O will bond with O-2-2 as H as H22OO

You may be tempted to write You may be tempted to write compounds and molecules compounds and molecules differently to balance an differently to balance an

equation- but you can’t! They equation- but you can’t! They bond as they bond.bond as they bond.

Things to Remember:Things to Remember:

Steps for Writing ReactionsSteps for Writing Reactions• Some steps for writing chemical reactions

1. Identify the type of reaction2. Predict the product(s) using the type of reaction3. Balance the equation

Don’t forget about the diatomic elements! (big 7) For example, Oxygen when by itself is O2 as a diatomic element; it is not found as just O.

In a compound or molecule, it can’t be a diatomic element because it’s not an element anymore, it’s a compound or molecule!

Synthesis ReactionsSynthesis Reactions

• Here is an example of a synthesis reaction

PracticePractice• Predict the products:

Write and balance the following synthesis reaction equations.

• Sodium metal reacts with chlorine gas Na(s) + Cl2(g) • Solid Magnesium reacts with fluorine gas Mg(s) + F2(g) • Aluminum metal reacts with fluorine gas Al(s) + F2(g)

Decomposition ReactionsDecomposition Reactions• An example of a decomposition reaction:

Decomposition ExceptionsDecomposition Exceptions

• Carbonates and chlorates are special case decomposition reactions that do not go to the elements.• Carbonates (CO3

2-) decompose to carbon dioxide and a metal oxide

• Example: CaCO3 CO2 + CaO• Chlorates (ClO3

-) decompose to oxygen gas and a metal chloride

• Example: 2 Al(ClO3)3 2 AlCl3 + 9 O2

• There are other special cases, but we will not explore those in Chemistry I

PracticePractice

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

• Solid Lead (IV) oxide decomposes PbO2(s)

• Aluminum nitride decomposes AlN(s)

PracticePractice

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

N2(g) + O2(g)

BaCO3(s)

Co(s)+ S(s)

NH3(g) + H2CO3(aq)

NI3(s)

(make Co be +3)

Nitrogen monoxide

Single Replacement ReactionsSingle Replacement Reactions• An example:

Single Replacement ReactionsSingle Replacement Reactions

• Write and balance the following single replacement reaction equation:

• Zinc metal reacts with aqueous hydrochloric acid

Zn(s) + HCl(aq)

Note: Zinc replaces the hydrogen ion in the reaction…Why?

Single Replacement ReactionsSingle Replacement Reactions• Sodium chloride solid reacts with fluorine gas __NaCl(s) + __F2(g) __NaF(s) +__Cl2(g)

Note that fluorine replaces chlorine in the compound

• Aluminum metal reacts with aqueous copper (II) nitrate

Al(s)+ Cu(NO3)2(aq)

Double Replacement ReactionsDouble Replacement Reactions

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

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

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

PracticePractice

• Predict the products. Balance the equation

1. HCl(aq) + AgNO3(aq)

2. CaCl2(aq) + Na3PO4(aq)

3. Pb(NO3)2(aq) + BaCl2(aq)

4. FeCl3(aq) + NaOH(aq)

5. H2SO4(aq) + NaOH(aq)

6. KOH(aq) + CuSO4(aq)

Combustion ReactionsCombustion Reactions

• Combustion reactions occur when a hydrocarbon reacts with oxygen gas.

• This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”:1) A Fuel (hydrocarbon)2) Oxygen to burn it with3) Something to ignite the reaction (spark)

CombustionCombustion

• Example• C5H12 + O2 CO2 + H2O

• Write the products and balance the following combustion reaction:• C10H22 + O2

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Mixed PracticeMixed Practice

• State the type, predict the products, and balance the following reactions:

1. BaCl2 + H2SO4

2. C6H12 + O2

3. Zn + CuSO4

4. Cs + Br2

5. FeCO3