Ch.11 - Liquids & Phase Changes

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.11 - Liquids & Phase Changes

Problem 10

Chapter 11, Problem 10

Which molecule has polar bonds but is nonpolar? (LO 8.6) (a) SF6 (b) SF2 (c) F2 (d) NF3

Verified step by step guidance

Step 1: Determine the polarity of the bonds in each molecule. A bond is polar if it is between two atoms with different electronegativities. In this case, SF6, SF2, and NF3 have polar bonds because Sulfur (S) and Nitrogen (N) have different electronegativities than Fluorine (F). F2 does not have a polar bond because both atoms are the same, so their electronegativities are equal.

Step 2: Determine the molecular geometry of each molecule. The molecular geometry can be determined by the VSEPR theory, which states that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion. SF6 has an octahedral shape, SF2 has a bent shape, and NF3 has a trigonal pyramidal shape.

Step 3: Determine the overall polarity of the molecule. A molecule is nonpolar if the dipole moments of its bonds cancel out. This happens when the molecule is symmetrical. In this case, SF6 is nonpolar because its octahedral shape is symmetrical, so the dipole moments of the S-F bonds cancel out. SF2 and NF3 are polar because their shapes (bent and trigonal pyramidal, respectively) are not symmetrical, so the dipole moments of their bonds do not cancel out.

Step 4: Therefore, the molecule that has polar bonds but is nonpolar is SF6.

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Key Concepts

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

Polarity of Bonds

Polarity in chemical bonds arises from the difference in electronegativity between two atoms. When one atom is more electronegative, it attracts the shared electrons more strongly, creating a dipole moment. A bond is considered polar if this dipole moment is significant, leading to partial positive and negative charges on the atoms involved.

Molecular Geometry

The three-dimensional arrangement of atoms in a molecule, known as molecular geometry, plays a crucial role in determining the overall polarity of the molecule. Even if a molecule contains polar bonds, its shape can lead to a cancellation of dipole moments, resulting in a nonpolar molecule. Common geometries include linear, trigonal planar, and tetrahedral.

Net Dipole Moment

The net dipole moment of a molecule is the vector sum of all individual dipole moments from its polar bonds. A molecule is classified as polar if it has a net dipole moment pointing in a specific direction. Conversely, if the dipole moments cancel each other out due to symmetry, the molecule is nonpolar, despite having polar bonds.

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Related Practice

Textbook Question

Consider a compound that has a melting point at 65 °C and a boiling point at 175 °C. Which of the following images represents a heating curve for the compound from 40 °C to 200 °C? (LO 11.5)

The DNA base thymine dissolves in water due to hydrogen bonding. Which of the following hydrogen bonds drawn between thymine and surrounding water molecules are valid? (LO 8.10) (a) I and II (b) I, II, IV (c) I, II, III (d) III and IV

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Textbook Question

Three identical tubes are filled with different liquids; water, ethylene glycol, and olive oil. A small steel sphere was dropped into the tube, and the time it took to fall to the bottom was recorded. Which property of liquids is responsible for the differences in time for the sphere to fall through the liquid? (LO 11.1)(a) Surface tension(b) Boiling point(c) Viscosity(d) Vapor pressure

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Textbook Question

Assume that you have a liquid in a cylinder equipped with a movable piston. There is no air in the cylinder, the volume of space above the liquid is 200 mL, and the equilibrium vapor pressure above the liquid is 28.0 mm Hg. What is the equilibrium pressure above the liquid when the volume of space is decreased from 200 mL to 100 mL at constant temperature?

Arrange the following molecules from lowest to highest boilingpoint. (LO 8.9)(I)

(II)

(III)

(IV)

(a) I 6 II 6 III 6 IV(b) II 6 III 6 I 6 IV(c) IV 6 II 6 III 6 I(d) IV 6 I 6 II 6 III

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