Open Question
Rationalize the difference in boiling points in each pair: (a) HF (20 °C) and HCl (-85 °C) (b) CHCl3 (61 °C) and CHBr3 (150 °C) (c) Br2 (59 °C) and ICl (97 °C)
Ch.11 - Liquids and Intermolecular Forces
Chapter 11, Problem 29
Look up and compare the normal boiling points and normal melting points of H2O and H2S. Based on these physical properties, which substance has stronger intermolecular forces? What kinds of intermolecular forces exist for each molecule?
Verified step by step guidance1
Step 1: Identify the normal boiling and melting points of H2O and H2S. H2O has a boiling point of 100°C and a melting point of 0°C, while H2S has a boiling point of -60°C and a melting point of -85°C.
Step 2: Compare the boiling and melting points of H2O and H2S. Notice that H2O has significantly higher boiling and melting points than H2S.
Step 3: Determine the types of intermolecular forces present in each molecule. H2O exhibits hydrogen bonding, dipole-dipole interactions, and London dispersion forces. H2S primarily exhibits dipole-dipole interactions and London dispersion forces.
Step 4: Analyze the strength of intermolecular forces based on boiling and melting points. Higher boiling and melting points in H2O suggest stronger intermolecular forces compared to H2S.
Step 5: Conclude that H2O has stronger intermolecular forces due to the presence of hydrogen bonding, which is absent in H2S, leading to higher boiling and melting points.
Related Practice
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. (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
Based on the type or types of intermolecular forces, predict the substance in each pair that has the higher boiling point: (d) phosgene (Cl2CO) or formaldehyde (H2CO)
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Textbook Question
A number of salts containing the tetrahedral polyatomic anion, BF4-, are ionic liquids, whereas salts containing the somewhat larger tetrahedral ion SO42- 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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Textbook Question
(b) What is the relationship between viscosity and temperature?
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