Redox and CombustionRedox and Combustion

Redox and Combustion:Redox and Combustion:At the conclusion of our time together, At the conclusion of our time together,

you should be able to:you should be able to:

1.1. Identify a basic combustion reactionIdentify a basic combustion reaction2.2. Balance a combustion reactionBalance a combustion reaction3.3. Show the change in oxidation numbers for Show the change in oxidation numbers for

a combustion reactiona combustion reaction

5. Combustion Reactions5. Combustion Reactions

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

• This is also called This is also called burning!!! In order to burn burning!!! In order to burn something you need the 3 something you need the 3 things in the “fire things in the “fire triangle”:triangle”:

•

1) A Fuel (hydrocarbon)1) A Fuel (hydrocarbon)2) Oxygen to burn it with2) Oxygen to burn it with3) Something to ignite the 3) Something to ignite the reaction (spark)reaction (spark)

Combustion ReactionsCombustion Reactions

• In general: In general: CCxxHHy y + O+ O2 2 CO CO2 2 + H+ H22OO

• Products in combustion are Products in combustion are ALWAYS carbon dioxide and ALWAYS carbon dioxide and water. (although incomplete water. (although incomplete burning does cause some burning does cause some by-products like carbon by-products like carbon monoxide)monoxide)

• Combustion is used to heat Combustion is used to heat homes and run automobiles homes and run automobiles (octane, as in gasoline, is (octane, as in gasoline, is CC88HH1818) )

Combustion ReactionsCombustion Reactions

Edgar Allen Poe’s drooping eyes and

mouth are potential signs of CO poisoning.

Combustion of Pentane:Combustion of Pentane:

Predict the products and balance the Predict the products and balance the reaction:reaction:

CC55HH1212 + O + O22 CO CO2 2 + H+ H22OO5 68

Predict the products and balance the Predict the products and balance the reaction:reaction:

CC33HH77OH + OOH + O22 CO CO2 2 + H+ H22OO

Combustion of PropanolCombustion of Propanol

2 6 89

Combustion of Methane and RedoxCombustion of Methane and Redox

CHCH44 + O + O22 CO CO2 2 + H+ H22OO

• Show the change in oxidation numbers:Show the change in oxidation numbers:• CC-4-4 C C+4+4

• Each carbon loses 8 electrons – oxidation, reducing agent

• O O O O2-2-

• Each oxygen gains 2 electrons – reduction, oxidizing agent

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Redox and Combustion:Redox and Combustion:Let’s see if you can:Let’s see if you can:

1.1. Identify a basic combustion reactionIdentify a basic combustion reaction2.2. Show the change in oxidation numbers for Show the change in oxidation numbers for

a combustion reactiona combustion reaction

PracticePractice

Predict the products and balance the Predict the products and balance the reaction of hexene burning in air:reaction of hexene burning in air:

CC66HH1212 + O + O2 2

CC66HH1212 + O + O22 CO CO2 2 + H+ H22OO• Show the change in oxidation numbers:Show the change in oxidation numbers:• CC-2-2 C C+4+4

• Each carbon loses 6 electrons – oxidation, reducing agent

• O O O O2-2-

• Each oxygen gains 2 electrons – reduction, oxidizing agent

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