Ch. 2 Chemistry Comes Alive

Marieb - Human Anatomy & Physiology 7th Edition

Marieb, Hoehn7th EditionHuman Anatomy & PhysiologyISBN: 9780805359091Not the one you use?Change textbook

Marieb, Hoehn 7th Edition

Ch. 2 Chemistry Comes Alive

Problem 14

Chapter 2, Problem 14

Which of the following covalently bonded molecules are polar?
(a)

(b)

(c)

(d)

Verified step by step guidance

Step 1: Understand molecular polarity by considering two main factors: the difference in electronegativity between bonded atoms and the molecular geometry (shape). A molecule is polar if it has polar bonds and an asymmetrical shape causing a net dipole moment.

Step 2: Analyze molecule (a) H-Cl. Chlorine is more electronegative than hydrogen, creating a polar covalent bond. Since this is a diatomic molecule, the polarity of the bond directly makes the molecule polar.

Step 3: Analyze molecule (b) CH4 (methane). Carbon and hydrogen have a small difference in electronegativity, and the molecule has a symmetrical tetrahedral shape. The bond dipoles cancel out, making methane nonpolar.

Step 4: Analyze molecule (c) CHCl3 (chloroform). Carbon is bonded to three chlorine atoms and one hydrogen atom. Chlorine is more electronegative than carbon and hydrogen, and the molecule is asymmetrical due to the different atoms attached, resulting in a polar molecule.

Step 5: Analyze molecule (d) N≡N (nitrogen gas). Both atoms are identical nitrogen atoms sharing electrons equally, so the bond is nonpolar and the molecule is nonpolar.

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Key Concepts

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

Molecular Polarity

Molecular polarity arises when there is an uneven distribution of electron density in a molecule, resulting in a dipole moment. This occurs if the molecule has polar bonds and an asymmetrical shape, causing one end to be partially positive and the other partially negative.

Electronegativity Difference

Electronegativity is the tendency of an atom to attract electrons in a bond. A significant difference in electronegativity between two bonded atoms creates a polar covalent bond, where electrons are shared unequally, leading to partial charges on the atoms.

Molecular Geometry and Symmetry

The shape of a molecule affects its overall polarity. Even if bonds are polar, a symmetrical arrangement can cancel out dipole moments, making the molecule nonpolar. Asymmetrical molecules with polar bonds tend to be polar overall.

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Related Practice

Textbook Question

Identify each reaction as one of the following:

a. A synthesis reaction

b. A decomposition reaction

c. An exchange reaction

(1) 2Hg + O₂ → 2HgO

(2) HCl + NaOH → NaCl + H₂O

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Textbook Question

A chemist, during the course of an analysis, runs across a chemical composed of carbon, hydrogen, and oxygen in the proportion 1:2:1 and having a six-sided molecular shape. It is probably:

a. A pentose

b. An amino acid

c. A fatty acid

d. A monosaccharide

e. A nucleic acid

Textbook Question

How many moles of aspirin, C₉H₈O₄, are in a bottle containing 450 g by weight? (Note: The approximate atomic weights of its atoms are C = 12, H = 1, and O = 16.)

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Textbook Question

Provide the atomic symbol for each of the following elements:

a. Calcium

b. Carbon

c. Hydrogen

d. Iron

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Textbook Question

Provide the atomic symbol for each of the following elements:

e. Nitrogen

f. Oxygen