Chapter 12: Problem 87
List these substances in order of increasing boiling point: $$ \mathrm{H}_{2} \mathrm{O}, \mathrm{Ne}, \mathrm{NH}_{3}, \mathrm{NaF}, \mathrm{SO}_{2} $$
Short Answer
Expert verified
Ne, SO2, NH3, H2O, NaF
Step by step solution
01
Understand Intermolecular Forces
To list substances in order of increasing boiling point, recognize and compare the types of intermolecular forces present in each substance. The main types of intermolecular forces are van der Waals (London dispersion forces), dipole-dipole interactions, hydrogen bonding, and ionic bonding. Generally, stronger intermolecular forces lead to higher boiling points.
02
Identify the Type of Intermolecular Forces in Each Substance
Identify the type of intermolecular forces for each substance: - Ne has only London dispersion forces (it is a noble gas).- H2O has hydrogen bonding due to the O-H bond.- NH3 has hydrogen bonding due to the N-H bond.- SO2 has dipole-dipole interactions as it is a polar molecule.- NaF has ionic bonds, which are strong intermolecular forces.
03
Arrange in Order of Increasing Boiling Points
Arrange the substances in order of increasing boiling points, based on the strength of their intermolecular forces. The order will be London dispersion forces (weakest), dipole-dipole, hydrogen bonding, and ionic bonds (strongest):- Noble gas (Ne)- Polar molecule with dipole-dipole interactions (SO2)- Molecule with hydrogen bonding (NH3)- Molecule with stronger hydrogen bonding due to higher electronegativity (H2O)- Ionic compound (NaF)
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with Vaia!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Intermolecular Forces
Introducing the concept of intermolecular forces is essential to grasp why different substances have varying boiling points. Simply put, intermolecular forces are the attractive forces between neighboring molecules. The strength of these forces is a key factor in determining the phase of matter, melting points, boiling points, and solubilities.
When comparing substances, those with stronger intermolecular forces require more energy, in the form of heat, to overcome these attractions and transition into a gas phase - thus, they have higher boiling points. On the flip side, weaker intermolecular bonds lead to lower boiling points, as less energy is needed for the molecules to break free from each other and vaporize.
When comparing substances, those with stronger intermolecular forces require more energy, in the form of heat, to overcome these attractions and transition into a gas phase - thus, they have higher boiling points. On the flip side, weaker intermolecular bonds lead to lower boiling points, as less energy is needed for the molecules to break free from each other and vaporize.
Hydrogen Bonding
Among the strongest of intermolecular forces is hydrogen bonding. It's a special case that occurs when a hydrogen atom is covalently bonded to a highly electronegative atom like nitrogen, oxygen, or fluorine, and is attracted to another electronegative atom in a different molecule.
In the context of our substances, both water (\r\(H_2O\)) and ammonia (\(NH_3\)) exhibit hydrogen bonding. However, water's hydrogen bonding is stronger due to oxygen's higher electronegativity compared to nitrogen. This means more energy is required to boil water than ammonia, hence water has a higher boiling point.
In the context of our substances, both water (\r\(H_2O\)) and ammonia (\(NH_3\)) exhibit hydrogen bonding. However, water's hydrogen bonding is stronger due to oxygen's higher electronegativity compared to nitrogen. This means more energy is required to boil water than ammonia, hence water has a higher boiling point.
Ionic Bonding
Moving onto ionic bonding, this type of force is even more powerful than hydrogen bonding. Ionic bonds form between atoms that transfer electrons from one to another, resulting in positively charged cations and negatively charged anions. These ions then attract each other with a significant force.
In sodium fluoride (NaF), the sodium (\r\(Na^+\)) and fluoride (\r\(F^-\)) ions are held together by ionic bonds. This strong attraction requires a large amount of energy to break, giving NaF a higher boiling point than substances with hydrogen bonding or weaker forces. It's the ionic bonds that place NaF at the top of the boiling point list among the given substances.
In sodium fluoride (NaF), the sodium (\r\(Na^+\)) and fluoride (\r\(F^-\)) ions are held together by ionic bonds. This strong attraction requires a large amount of energy to break, giving NaF a higher boiling point than substances with hydrogen bonding or weaker forces. It's the ionic bonds that place NaF at the top of the boiling point list among the given substances.
Dipole-Dipole Interactions
Dipole-dipole interactions occur in polar molecules where there is an uneven distribution of electron density. This causes a permanent dipole with positive and negative ends, which attract the opposite ends of nearby molecules in a comparable manner.
Sulfur dioxide (\(SO_2\)) is a perfect example with a bent molecular geometry causing a polar structure, leading to dipole-dipole interactions. These are stronger than London dispersion forces but weaker than hydrogen bonding, placing \(SO_2\) above neon in terms of boiling point within our list of substances.
Sulfur dioxide (\(SO_2\)) is a perfect example with a bent molecular geometry causing a polar structure, leading to dipole-dipole interactions. These are stronger than London dispersion forces but weaker than hydrogen bonding, placing \(SO_2\) above neon in terms of boiling point within our list of substances.
London Dispersion Forces
The weakest of the bunch are London dispersion forces, also known as van der Waals forces. These are temporary dipoles that occur when electrons within an atom or molecule are unevenly distributed, creating a temporary polarity. All molecules experience these forces, but they are the only type for nonpolar molecules such as neon (Ne).
Given that these forces are fleeting and weak, they require the least amount of energy to overcome, reflecting in the lowest boiling points for substances that depend solely on them, like Ne. It is thus the dispersion forces that put Ne at the lowest end of the boiling point spectrum.
Given that these forces are fleeting and weak, they require the least amount of energy to overcome, reflecting in the lowest boiling points for substances that depend solely on them, like Ne. It is thus the dispersion forces that put Ne at the lowest end of the boiling point spectrum.