Exploring Alkanes and Their Reactions

Which of the following is a general property of alkanes?

• They are highly reactive.

• They are non-polar.

• They are soluble in water.

• They have a high boiling point.

Answer explanation

Alkanes are generally non-polar due to their hydrocarbon structure, which lacks significant electronegative atoms. This non-polarity leads to low solubility in water and contributes to their relatively low reactivity compared to other organic compounds.

What is the main product of the complete combustion of alkanes?

• Carbon monoxide and water

• Carbon dioxide and water

• Carbon and water

• Methane and water

Answer explanation

The complete combustion of alkanes primarily produces carbon dioxide and water. This occurs when alkanes react with sufficient oxygen, resulting in these two products, making 'Carbon dioxide and water' the correct choice.

Which of the following is an example of an alkane isomer?

• Butane and isobutane

• Ethene and ethyne

• Propene and propane

• Methanol and ethanol

Answer explanation

Butane and isobutane are structural isomers, differing in the arrangement of carbon atoms. Ethene and ethyne are alkenes and alkynes, while propene and propane are also not isomers. Methanol and ethanol are alcohols, not alkanes.

• Pentane

• Butane

• Hexane

• Propane

Answer explanation

The molecular formula C5H12 corresponds to an alkane with five carbon atoms. According to IUPAC nomenclature, this compound is named pentane, distinguishing it from butane (4 carbons), hexane (6 carbons), and propane (3 carbons).

Which of the following is a common use of alkanes?

• As a solvent in water-based paints

• As a fuel for heating and cooking

• As a refrigerant

• As a food preservative

Answer explanation

Alkanes are commonly used as fuels for heating and cooking due to their high energy content and clean-burning properties. Other options listed are not typical uses for alkanes.

What is the molecular formula for hexane?

Answer explanation

Hexane is an alkane with six carbon atoms. Its molecular formula is C6H14, which corresponds to the correct choice. The other options represent different alkanes with fewer or more carbon atoms.

Which of the following statements about alkane combustion is true?

• It produces only carbon monoxide.

• It requires a catalyst.

• It is an exothermic reaction.

• It does not require oxygen.

Answer explanation

The correct statement is that alkane combustion is an exothermic reaction, meaning it releases energy in the form of heat. The other options are incorrect as combustion produces carbon dioxide and requires oxygen, not a catalyst.

• 1

• 2

• 3

• 4

Answer explanation

The molecular formula C4H10 corresponds to butane. There are two structural isomers: n-butane (a straight chain) and isobutane (a branched chain). Therefore, the correct answer is 2.

Which of the following alkanes is a gas at room temperature?

• Octane

• Methane

• Hexane

• Nonane

Answer explanation

Methane is the smallest alkane and is a gas at room temperature, while octane, hexane, and nonane are larger alkanes that are liquids or solids at room temperature.

What is the main reason alkanes are used as fuels?

• They are highly reactive.

• They have a high energy content.

• They are easily soluble in water.

• They are non-flammable.

Answer explanation

Alkanes are used as fuels primarily because they have a high energy content, which allows for efficient combustion and energy release. The other options are incorrect as they do not accurately describe alkanes' properties.