Based on their composition and structure, list CH 2 Cl 2 , CH 3 CH 2 CH 3 , and CH 3 CH 2 OH in order of (a) increasing intermolecular forces (c) increasing surface tension

Hey everyone, we're asked to arrange the following compounds in order of decreasing surface tension. Now we've learned that as our inter molecular forces increase, our surface tension will also increase. So let's go ahead and compare our inter molecular forces for each one. We can see that we have an oxygen here, which means that we have hydrogen bonding. And this is going to be one of our strongest inter molecular forces. So this means that this compound will have the largest surface tension due to that hydrogen bonding. Next. We know that the compound with our chlorine will be next. And the reason why is because this compound exhibits dipole dipole interactions and this occurs between two polar covalin compounds. And lastly we have our last compound which is filled with hydrocarbons and because it is filled with hydrocarbons, the only inner molecular force present here is going to be dispersion forces, which is going to be our weakest inner molecular force. So this is going to be our final answer for this question. Now I hope that made sense. And let us know if you have any questions

Ch.11 - Liquids and Intermolecular Forces

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Brown 15th Edition

Ch.11 - Liquids and Intermolecular Forces

Problem 36a,c

Chapter 11, Problem 36a,c

Based on their composition and structure, list CH₂Cl₂, CH₃CH₂CH₃, and CH₃CH₂OH in order of (a) increasing intermolecular forces (c) increasing surface tension

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Identify the molecular structure of each compound: CH$_2$Cl$_2$ (dichloromethane), CH$_3$CH$_2$CH$_3$ (propane), and CH$_3$CH$_2$OH (ethanol).

Consider the types of intermolecular forces present in each compound. CH$_2$Cl$_2$ has dipole-dipole interactions due to its polar nature, CH$_3$CH$_2$CH$_3$ has only London dispersion forces as it is nonpolar, and CH$_3$CH$_2$OH has hydrogen bonding due to the presence of an -OH group.

Recall that surface tension is influenced by the strength of intermolecular forces: stronger intermolecular forces result in higher surface tension.

Compare the strength of intermolecular forces: hydrogen bonding (strongest) > dipole-dipole interactions > London dispersion forces (weakest).

Arrange the compounds in order of increasing surface tension based on the strength of their intermolecular forces: CH$_3$CH$_2$CH$_3$ (weakest) < CH$_2$Cl$_2$ < CH$_3$CH$_2$OH (strongest).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Surface Tension

Surface tension is a physical property of liquids that describes the elastic-like force at the surface, caused by the cohesive forces between liquid molecules. It is influenced by intermolecular forces, such as hydrogen bonding and van der Waals forces. Liquids with stronger intermolecular forces typically exhibit higher surface tension, as the molecules at the surface are pulled inward more strongly.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion between molecules. They include hydrogen bonds, dipole-dipole interactions, and London dispersion forces. The type and strength of these forces significantly affect the physical properties of substances, including boiling point, melting point, and surface tension. For example, molecules with hydrogen bonding, like alcohols, generally have higher surface tension than non-polar molecules.

Molecular Structure and Polarity

The molecular structure and polarity of a compound play a crucial role in determining its physical properties. Polar molecules, which have a significant difference in electronegativity between atoms, tend to have stronger intermolecular forces compared to non-polar molecules. In the context of the given compounds, the presence of polar functional groups, such as hydroxyl (-OH) in CH3CH2OH, increases surface tension due to enhanced hydrogen bonding compared to non-polar hydrocarbons.

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Molecular Polarity

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Textbook Question

The generic structural formula for a 1-alkyl-3-methylimid- azolium cation is where R is a -CH2(CH2)nCH3 alkyl group. The melting points of the salts that form between 1-alkyl-3-methylimidazolium cation and the PF6- anion are as follows: R = CH2CH3 (m.p. = 60 °C), R = CH2CH2CH3 (m.p. = 40 °C), r = CH2CH2CH2CH3 (m.p. = 10 °C), and R = CH2CH2CH2CH2CH2CH3 (m.p. = -61 °C). Why does the melting point decrease as the length of alkyl group increases?

Textbook Question

(b) What is the relationship between viscosity and temperature?

Textbook Question

Liquids can interact with flat surfaces just as they can with capillary tubes; the cohesive forces within the liquid can be stronger or weaker than the adhesive forces between liquid and surface:

(b) Which of these diagrams, i or ii, rep- resents what happens when water is on a nonpolar surface?

Textbook Question

The boiling points, surface tensions, and viscosities of water and several alcohols are listed in the following table:

b. How do you explain the fact that propanol and ethylene glycol have similar molecular weights (60 vs. 62 amu), yet the viscosity of ethylene glycol is more than 10 times larger than propanol?

Based on their composition and structure, list CH2Cl2, CH3CH2CH3, and CH3CH2OH in order of (a) increasing intermolecular forces (c) increasing surface tension

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Key Concepts

Surface Tension

Intermolecular Forces

Molecular Structure and Polarity

Based on their composition and structure, list CH₂Cl₂, CH₃CH₂CH₃, and CH₃CH₂OH in order of (a) increasing intermolecular forces (c) increasing surface tension