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Ch.8 - Basic Concepts of Chemical Bonding
All textbooksBrown 14th EditionCh.8 - Basic Concepts of Chemical BondingProblem 72
Chapter 8, Problem 72

State whether each of these statements is true or false. (a) An oxygen–oxygen double bond is shorter than an oxygen–oxygen single bond. (b) The C—C bond in ethene is longer than the C—C bond in polyethene.

Verified step by step guidance
1
Step 1: Understand the nature of chemical bonds. A double bond involves the sharing of two pairs of electrons between atoms, while a single bond involves only one pair of electrons.
Step 2: Analyze statement (a). Compare the bond lengths of oxygen-oxygen double bonds and single bonds. Double bonds are generally shorter than single bonds due to the increased electron sharing, which pulls the atoms closer together.
Step 3: Evaluate statement (b). Consider the structure of ethene (C2H4), which contains a carbon-carbon double bond, and polyethene, which is a polymer made up of carbon-carbon single bonds.
Step 4: Compare the bond lengths in statement (b). Double bonds, like the C=C bond in ethene, are shorter than single bonds, such as the C-C bonds in polyethene, due to the same principle of increased electron sharing.
Step 5: Conclude the truth value of each statement based on the bond length comparisons: (a) is true because double bonds are shorter than single bonds, and (b) is false because the C=C bond in ethene is shorter than the C-C bond in polyethene.

Key Concepts

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

Bond Length and Bond Order

Bond length is the distance between the nuclei of two bonded atoms. Generally, as bond order increases (from single to double to triple bonds), bond length decreases due to greater electron sharing, which pulls the atoms closer together. Therefore, a double bond is typically shorter than a single bond.
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Types of Carbon-Carbon Bonds

In organic chemistry, the type of carbon-carbon bond affects the properties of the molecule. Ethene (C2H4) contains a double bond (C=C), while polyethene consists of long chains of single bonds (C—C). The presence of double bonds in ethene results in a shorter bond length compared to the single bonds in polyethene.
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Comparative Bond Lengths

When comparing bond lengths, it is essential to consider the type of bonding and molecular structure. Generally, double bonds are shorter than single bonds, and within a polymer like polyethene, the C—C bonds are longer due to the absence of double bonding. This principle helps in determining the truth of the statements regarding bond lengths.
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Related Practice
Textbook Question

Some chemists believe that satisfaction of the octet rule should be the top criterion for choosing the dominant Lewis structure of a molecule or ion. Other chemists believe that achieving the best formal charges should be the top criterion. Consider the dihydrogen phosphate ion, H2PO4-, in which the H atoms are bonded to O atoms. (b) What is the predicted dominant Lewis structure if achieving the best formal charges is the top criterion?

Textbook Question

State whether each of these statements is true or false. (a) The longer the bond, the stronger the bond. (c) A typical double bond length is in the 500–1000 pm range.

Textbook Question

State whether each of these statements is true or false. (e) The longer the bond, the more energy is stored chemical bonds.