Problem 81 - Chemistry The Central Science

Question

(a) What is a monomer? (b) Which of these molecules can be used as a monomer: ethanol, ethene (also called ethylene), methane?

Step-by-Step Solution

Answer

(a) A monomer is a small molecule that can bind to other similar molecules to form a larger and more complex structure called a polymer, through polymerization reactions. (b) Among ethanol (\(C_2H_5OH\)), ethene (\(C_2H_4\), also called ethylene), and methane (\(CH_4\)), only ethene can be used as a monomer, as it has a double bond that can break to form single bonds, allowing it to undergo polymerization reactions. Ethanol and methane lack reactive sites or functional groups necessary for polymerization reactions.

Step 1: Defining a Monomer

A monomer is a small molecule that can bind to other similar molecules to form a larger and more complex structure called a polymer. Monomers have the ability to join together through chemical bonds and undergo a polymerization reaction to form long chains or three-dimensional networks.

Step 2: Identifying Monomers

To identify which of the given molecules can be used as a monomer, we need to know their structures and see if they can undergo polymerization reactions. 1. Ethanol (\(C_2H_5OH\)): Ethanol has the molecular formula \(C_2H_5OH\). It is a simple alcohol with an -OH (hydroxyl) group attached to one of its carbon atoms. Ethanol cannot undergo polymerization reactions and, therefore, is not considered a monomer. 2. Ethene (\(C_2H_4\), also called ethylene): Ethene has the molecular formula \(C_2H_4\). It is an alkene with a double bond between the two carbon atoms (\(C=C\)). This double bond can break easily to form single bonds, which can then bond with other ethene molecules. As a result, ethene can undergo polymerization reactions and is considered a monomer. 3. Methane (\(CH_4\)): Methane has the molecular formula \(CH_4\). It is the simplest alkane, with a single carbon atom bonded to four hydrogen atoms. Methane lacks any multiple bonds, functional groups, or reactive sites to undergo polymerization reactions. Therefore, methane is not considered a monomer.

Step 3: Conclusion

Based on the molecular structures and reactivity of the given compounds, only ethene (ethylene) can be considered a monomer as it can undergo polymerization reactions to form polymers. Ethanol and methane cannot be used as monomers due to their lack of a reactive site or a functional group that allows them to undergo polymerization reactions.