Exploring Alkenes and Their Reactions

Answer explanation

The hydrogenation of ethene (C2H4) adds hydrogen across the double bond, converting it to ethane (C2H6) in the presence of a nickel catalyst. Therefore, the correct product is ethane.

Which of the following is a common catalyst used in the hydrogenation of alkenes?

• Iron

• Nickel

• Copper

• Zinc

Answer explanation

Nickel is a common catalyst used in the hydrogenation of alkenes due to its effectiveness in facilitating the addition of hydrogen across double bonds. Other options like iron, copper, and zinc are not typically used for this reaction.

What type of reaction is the polymerization of alkenes?

• Addition reaction

• Substitution reaction

• Elimination reaction

• Redox reaction

Answer explanation

The polymerization of alkenes is an addition reaction because it involves the addition of monomer units to form a polymer without the loss of any small molecules. This distinguishes it from substitution, elimination, or redox reactions.

Which of the following is a product of the polymerization of ethene?

• Polyvinyl chloride (PVC)

• Polyethylene

• Polystyrene

• Polypropylene

Answer explanation

Polyethylene is the direct product of the polymerization of ethene, where multiple ethene molecules combine to form long chains. The other options are derived from different monomers.

What is the general formula for the polymerization of an alkene?

Answer explanation

The general formula for the polymerization of an alkene is nC_nH_{2n} ightarrow (C_nH_{2n})_n. This indicates that n moles of the alkene combine to form a polymer with the same general formula, maintaining the same number of carbon and hydrogen atoms.

What is the product when ethene reacts with chlorine?

• Ethyl chloride

• Dichloroethane

• Chloroethene

• Trichloroethane

Answer explanation

When ethene reacts with chlorine, it undergoes an addition reaction, resulting in the formation of dichloroethane, where two chlorine atoms are added across the double bond of ethene.

Which of the following is true about the reaction of alkenes with halogens?

• It is a substitution reaction.

• It is an addition reaction.

• It is a condensation reaction.

• It is a decomposition reaction.

Answer explanation

The reaction of alkenes with halogens is an addition reaction, where halogen atoms are added across the double bond of the alkene, resulting in a saturated compound. This distinguishes it from substitution, condensation, and decomposition reactions.

What is the main characteristic of the hydrogenation reaction of alkenes?

• It involves the addition of water.

• It involves the addition of hydrogen.

• It involves the removal of hydrogen.

• It involves the addition of oxygen.

Answer explanation

The hydrogenation reaction of alkenes is characterized by the addition of hydrogen to the carbon-carbon double bond, converting it into a single bond. This process increases the saturation of the molecule.

Which of the following alkenes will produce a polymer when subjected to polymerization?

• Ethene

• Methane

• Ethyne

• Benzene

Answer explanation

Ethene is an alkene with a double bond that can undergo polymerization to form polyethylene, a common polymer. Methane is an alkane, ethyne is an alkyne, and benzene is an aromatic compound, none of which readily form polymers.

What is the result of the reaction between propene and bromine?

• 1,2-Dibromopropane

• 1-Bromopropane

• 2-Bromopropane

• 1,3-Dibromopropane

Answer explanation

The reaction between propene and bromine results in the addition of bromine across the double bond, forming 1,2-dibromopropane. This is due to the electrophilic addition mechanism, where bromine adds to the first and second carbon atoms.