reactions of alkanes

Physical properties of alkanes

By Remya Radhakrishnan

learning objective

​Understand how to know the trend in colour, boiling point and viscosity of the main fractions

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Key words

boiling points

viscous

volatile

flammability​

Subject | Subject

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Open Ended

Identify and write the name of the structure

Multiple Choice

In the fractional distillation of crude oil, where is the hottest part of the fractionating column?

• top of the tower

• middle of the tower

• bottom of the tower

Multiple Choice

Which fraction leaves the tower at the very top?

• fuel oil

• refinery gas

• petrol

Multiple Choice

Which is a use for kerosene (paraffin)?

• fuel for cars

• construction of roads

• aircraft fuel

Multiple Choice

Where do the longest hydrocarbon molecules condense?

• At the top of the tower

• At the bottom of the tower

• They do not condense at all and remain a gas

Multiple Choice

Which is the main compound in natural gas?

• ethane

• methane

• propane

Multiple Choice

Which of the following is the most viscous?

• kerosene

• fuel oil

• petrol

• bitumen

Multiple Choice

Which of the following is most volatile

• refinery gas

• petrol

• kerosene

• fuel oil

Multiple Choice

The colour the the fractions becomer darker

• as the size of the molecules decreases

• as the size of the molecules increases

Multiple Choice

Which fraction has the longest chain length.

• petrol

• kerosene

• fuel oil

• diesel

Multiple Choice

Which of the fraction is highly flammable?

• petrol

• refinery gas

• diesel

• kerosene

​Combustion

Burning in the presence of oxygen. All alkanes burn in air or oxygen.

​

Combustion can be classified as Complete combustion and incomplete combustion. ​

Subject | Subject

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​Complete combustion

If there is enough oxygen, alkanes burn completely to give carbon dioxide and water.

Subject | Subject

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Multiple Select

Identify the correct balanced chemical equation for the complete combustion of ethane.

• 2C₂H6 + 7O₂ --> 4CO₂ + 6H₂O

• C₂H6 + O₂ --> CO + H₂O

• C₂H6 + 3.5 O₂ --> 2CO₂ + 3H₂O

• C₂H6 + 3O₂ --> 2CO₂ + 3H₂O

Open Ended

Write the complete balanced chemical equations for methane and butane.

​Incomplete combustion

If there isn't enough oxygen, there is incomplete combustion of the hydrocarbon and obtain carbon monoxide or carbon(soot) instead of carbon dioxide.

Subject | Subject

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Open Ended

Write equations for incomplete combustion of butane to form carbon monoxide and watervapour

Multiple Choice

Which of the following is an alkane?

• ethanol

• cyclohexane

• propene

Multiple Choice

Looking at the chemical formulae of these compounds, which is an alkane?

• C₃H₈

• C₂H₄

• C₅H₁₀

Multiple Choice

What is the name of the alkane which has the formula C₄H₁₀?

• ethane

• octane

• butene

• butane

Open Ended

Alkanes are saturated hydrocarbons. What does this mean?

Multiple Choice

Which is a correct statement about incomplete combustion?

• Poisonous carbon monoxide may be produced

• It releases more energy than complete combustion

• It is cleaner than complete combustion

Multiple Choice

Which of these equations shows complete combustion?

• C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

• C₃H₈ + 3½O₂ → 3CO + 4H₂O

• C₃H₈ + 2O₂ → 3C + 4H₂O

Open Ended

Write a balanced chemical equation for the incomplete combustion of pentane forming carbon monoxide and water.

Open Ended

Alkenes more reactive than alkanes.

Yes or no, give an explanation for your answer.