Answer :
To determine which compound exhibits the highest viscosity at 298 K, we need to consider the factors that affect viscosity. Viscosity is a measure of a fluid's resistance to flow, and it is influenced by the strength of intermolecular forces present in the substance. Molecules with stronger intermolecular forces will generally have higher viscosities.
One of the most significant types of intermolecular forces is hydrogen bonding. Hydrogen bonds occur when a hydrogen atom is directly bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine), allowing for significant intermolecular attractions.
Let's analyze each of the given compounds in terms of their ability to form hydrogen bonds and other types of intermolecular forces:
A. [tex]\( \text{HOCH}_2\text{CH}_2\text{OH} \)[/tex] (ethylene glycol)
- This molecule contains two hydroxyl (-OH) groups. Hydroxyl groups are capable of forming hydrogen bonds both as hydrogen bond donors and acceptors. Because there are two -OH groups, this molecule can form multiple hydrogen bonds, significantly increasing its intermolecular attractions and therefore its viscosity.
B. [tex]\( \text{CH}_3 \text{OCH}_3 \)[/tex] (dimethyl ether)
- This molecule has an oxygen atom that can act as a hydrogen bond acceptor, but it does not contain any hydrogen atoms bonded to highly electronegative atoms that would allow it to act as a hydrogen bond donor. Thus, it has weaker intermolecular forces than molecules capable of hydrogen bonding.
C. [tex]\( \text{CH}_3 \text{OH} \)[/tex] (methanol)
- Methanol contains one hydroxyl (-OH) group, which allows it to form hydrogen bonds. However, it has fewer sites for hydrogen bonding compared to ethylene glycol.
D. [tex]\( \text{CH}_3 \text{Br} \)[/tex] (methyl bromide)
- This molecule does not have the ability to form hydrogen bonds. The primary intermolecular force here would be dipole-dipole interactions, which are weaker than hydrogen bonds.
E. [tex]\( \text{CH}_2 \text{Cl}_2 \)[/tex] (dichloromethane)
- This molecule also cannot form hydrogen bonds. It primarily exhibits dipole-dipole interactions and London dispersion forces, which are weaker than hydrogen bonds.
Based on the assessment of each compound's ability to engage in hydrogen bonding and other intermolecular forces, we can conclude that the molecule with the highest capacity for forming strong intermolecular bonds (hydrogen bonds) is A [tex]\( \text{HOCH}_2\text{CH}_2\text{OH} \)[/tex]. Ethylene glycol has multiple -OH groups, thereby enabling extensive hydrogen bonding.
Hence, the compound that should exhibit the highest viscosity at 298 K is:
A [tex]\( \text{HOCH}_2\text{CH}_2\text{OH} \)[/tex].
One of the most significant types of intermolecular forces is hydrogen bonding. Hydrogen bonds occur when a hydrogen atom is directly bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine), allowing for significant intermolecular attractions.
Let's analyze each of the given compounds in terms of their ability to form hydrogen bonds and other types of intermolecular forces:
A. [tex]\( \text{HOCH}_2\text{CH}_2\text{OH} \)[/tex] (ethylene glycol)
- This molecule contains two hydroxyl (-OH) groups. Hydroxyl groups are capable of forming hydrogen bonds both as hydrogen bond donors and acceptors. Because there are two -OH groups, this molecule can form multiple hydrogen bonds, significantly increasing its intermolecular attractions and therefore its viscosity.
B. [tex]\( \text{CH}_3 \text{OCH}_3 \)[/tex] (dimethyl ether)
- This molecule has an oxygen atom that can act as a hydrogen bond acceptor, but it does not contain any hydrogen atoms bonded to highly electronegative atoms that would allow it to act as a hydrogen bond donor. Thus, it has weaker intermolecular forces than molecules capable of hydrogen bonding.
C. [tex]\( \text{CH}_3 \text{OH} \)[/tex] (methanol)
- Methanol contains one hydroxyl (-OH) group, which allows it to form hydrogen bonds. However, it has fewer sites for hydrogen bonding compared to ethylene glycol.
D. [tex]\( \text{CH}_3 \text{Br} \)[/tex] (methyl bromide)
- This molecule does not have the ability to form hydrogen bonds. The primary intermolecular force here would be dipole-dipole interactions, which are weaker than hydrogen bonds.
E. [tex]\( \text{CH}_2 \text{Cl}_2 \)[/tex] (dichloromethane)
- This molecule also cannot form hydrogen bonds. It primarily exhibits dipole-dipole interactions and London dispersion forces, which are weaker than hydrogen bonds.
Based on the assessment of each compound's ability to engage in hydrogen bonding and other intermolecular forces, we can conclude that the molecule with the highest capacity for forming strong intermolecular bonds (hydrogen bonds) is A [tex]\( \text{HOCH}_2\text{CH}_2\text{OH} \)[/tex]. Ethylene glycol has multiple -OH groups, thereby enabling extensive hydrogen bonding.
Hence, the compound that should exhibit the highest viscosity at 298 K is:
A [tex]\( \text{HOCH}_2\text{CH}_2\text{OH} \)[/tex].
