Based on the type or types of intermolecular forces, predict the substance in each pair that has the higher boiling point: (a) propane (C 3 H 8 ) or n-butane (C 4 H 10 ) (b) diethyl ether (CH 3 CH 2 OCH 2 CH 3 ) or 1-butanol (CH 3 CH 2 CH 2 CH 2 OH) (c) sulfur dioxide (SO 2 ) or sulfur trioxide (SO 3 ) (d) phosgene (Cl 2 CO) or formaldehyde (H 2 CO)

Hey everyone, we're asked to identify the compound that has a higher boiling point between metal for me or formal chloride first, let's go ahead and draw this out. Now, looking at our two structures, we can see that we have disciple disciple interactions for both. And since we only have dipole dipole interactions for both, we have to compare their molecular masses in order to determine which one has a higher boiling point. And since formal chloride has the larger molecular mass, this means that it will have the higher boiling point. And another reason why our method format doesn't have a higher boiling point than our formal chloride is because it doesn't have the capacity to hydrogen bond and our hydrogen is not bound to a strongly electro negative element. So our final answer here is going to be formal chloride with the higher boiling point. So I hope that made sense. And let us know if you have any questions.

Ch.11 - Liquids and Intermolecular Forces

Brown - Chemistry: The Central Science 14th Edition

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Brown 14th Edition

Ch.11 - Liquids and Intermolecular Forces

Problem 28

Chapter 11, Problem 28

Based on the type or types of intermolecular forces, predict the substance in each pair that has the higher boiling point: (a) propane (C₃H₈) or n-butane (C₄H₁₀) (b) diethyl ether (CH₃CH₂OCH₂CH₃) or 1-butanol (CH₃CH₂CH₂CH₂OH) (c) sulfur dioxide (SO₂) or sulfur trioxide (SO₃) (d) phosgene (Cl₂CO) or formaldehyde (H₂CO)

Verified step by step guidance

Identify the types of intermolecular forces present in each molecule. Phosgene (Cl₂CO) and formaldehyde (H₂CO) both exhibit dipole-dipole interactions due to their polar nature.

Consider the possibility of hydrogen bonding in each molecule. Formaldehyde (H₂CO) has hydrogen atoms bonded to oxygen, which can participate in hydrogen bonding.

Assess the molecular weights and size of the molecules. Phosgene (Cl₂CO) is heavier and larger compared to formaldehyde (H₂CO), which can influence the strength of the dipole-dipole interactions.

Compare the overall strength of the intermolecular forces in each molecule. The presence of hydrogen bonding in formaldehyde (H₂CO) generally leads to stronger intermolecular forces compared to just dipole-dipole interactions in phosgene (Cl₂CO).

Predict the substance with the higher boiling point based on the stronger intermolecular forces. In this case, formaldehyde (H₂CO) is likely to have a higher boiling point due to the presence of hydrogen bonding.

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Key Concepts

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

Intermolecular Forces

Intermolecular forces are the attractive forces between molecules that influence physical properties such as boiling and melting points. The main types include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. Understanding these forces helps predict how substances behave under different conditions, particularly in terms of phase changes.

Boiling Point

The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure, allowing it to transition from liquid to gas. Substances with stronger intermolecular forces typically have higher boiling points because more energy is required to overcome these attractions. Thus, comparing boiling points can provide insights into the nature of the intermolecular forces present.

Polarity and Molecular Structure

Polarity refers to the distribution of electrical charge over the atoms in a molecule, which affects its intermolecular interactions. Molecules like formaldehyde (H2CO) are polar due to the presence of a carbonyl group, leading to dipole-dipole interactions. In contrast, phosgene (Cl2CO) has a more complex structure that can influence its overall polarity and the types of intermolecular forces it exhibits.

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Ethylene glycol (HOCH2CH2OH), the major substance in antifreeze, has a normal boiling point of 198 °C. By comparison, ethyl alcohol (CH3CH2OH) boils at 78 °C at atmospheric pressure. Ethylene glycol dimethyl ether (CH3OCH2CH2OCH3) has a normal boiling point of 83 °C, and ethyl methyl ether (CH3CH2OCH3) has a nomral boiling point of 11 °C. (a) Explain why replacement of a hydrogen on the oxygen by a CH3 group generally results in a lower boiling point.

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Textbook Question

Ethylene glycol (HOCH₂CH₂OH), the major substance in antifreeze, has a normal boiling point of 198 °C. By comparison, ethyl alcohol (CH₃CH₂OH) boils at 78 °C at atmospheric pressure. Ethylene glycol dimethyl ether (CH₃OCH₂CH₂OCH₃) has a normal boiling point of 83 °C, and ethyl methyl ether (CH3CH2OCH3) has a nomral boiling point of 11 °C. (b) What are the major factors responsible for the difference in boiling points of the two ethers?

Textbook Question

A number of salts containing the tetrahedral polyatomic anion, BF₄^-, are ionic liquids, whereas salts containing the somewhat larger tetrahedral ion SO₄^2-do not form ionic liquids. Explain this observation.

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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?

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