Chapter 12 - CHAPTER 12 INTERMOLECULAR FORCES AND LIQUIDS...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
CHAPTER 12 INTERMOLECULAR FORCES AND LIQUIDS AND SOLIDS 12.7 ICl has a dipole moment and Br 2 does not. The dipole moment increases the intermolecular attractions between ICl molecules and causes that substance to have a higher melting point than bromine. 12.8 Strategy: Classify the species into three categories: ionic, polar (possessing a dipole moment), and nonpolar. Keep in mind that dispersion forces exist between all species. Solution: The three molecules are essentially nonpolar. There is little difference in electronegativity between carbon and hydrogen. Thus, the only type of intermolecular attraction in these molecules is dispersion forces. Other factors being equal, the molecule with the greater number of electrons will exert greater intermolecular attractions. By looking at the molecular formulas you can predict that the order of increasing boiling points will be CH 4 < C 3 H 8 < C 4 H 10 . On a very cold day, propane and butane would be liquids (boiling points 44.5 ° C and 0.5 ° C, respectively); only methane would still be a gas (boiling point 161.6 ° C). 12.9 All are tetrahedral (AB 4 type) and are nonpolar. Therefore, the only intermolecular forces possible are dispersion forces. Without worrying about what causes dispersion forces, you only need to know that the strength of the dispersion force increases with the number of electrons in the molecule (all other things being equal). As a consequence, the magnitude of the intermolecular attractions and of the boiling points should increase with increasing molar mass. 12.10 (a) Benzene (C 6 H 6 ) molecules are nonpolar. Only dispersion forces will be present. (b) Chloroform (CH 3 Cl) molecules are polar (why?). Dispersion and dipole-dipole forces will be present. (c) Phosphorus trifluoride (PF 3 ) molecules are polar. Dispersion and dipole-dipole forces will be present. (d) Sodium chloride (NaCl) is an ionic compound. Ion-ion (and dispersion) forces will be present. (e) Carbon disulfide (CS 2 ) molecules are nonpolar. Only dispersion forces will be present. 12.11 The center ammonia molecule is hydrogen bonded to two other ammonia molecules. HNH H H NHN H H H H 12.12 In this problem you must identify the species capable of hydrogen bonding among themselves, not with water. In order for a molecule to be capable of hydrogen bonding with another molecule like itself, it must have at least one hydrogen atom bonded to N, O, or F. Of the choices, only (e) CH 3 COOH (acetic acid) shows this structural feature. The others cannot form hydrogen bonds among themselves.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CHAPTER 12: INTERMOLECULAR FORCES AND LIQUIDS AND SOLIDS 239 12.13 CO 2 is a nonpolar molecular compound. The only intermolecular force present is a relatively weak dispersion force (small molar mass). CO 2 will have the lowest boiling point. CH 3 Br is a polar molecule. Dispersion forces (present in all matter) and dipole dipole forces will be present.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 17

Chapter 12 - CHAPTER 12 INTERMOLECULAR FORCES AND LIQUIDS...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online