Chapter 5: Problem 85

Is the bond between the carbon atoms in the ethylene molecule of Problem \(5.84\) stronger or weaker than the bond in acetylene, \(\mathrm{C}_{2} \mathrm{H}_{2}\) (WorkPatch 5.7)? Explain fully.

Short Answer

Expert verified

The bond between the carbon atoms in the ethylene molecule (C2H4) is weaker than the bond in acetylene (C2H2) because ethylene has a double bond, whereas acetylene has a triple bond between the carbon atoms. Triple bonds are stronger than double bonds due to the greater number of shared electron pairs, which results in a stronger electrostatic attraction between the atoms involved in the bond.

Step by step solution

Identify the type of bonds in each molecule

First, we need to identify the type of bond present between carbon atoms in ethylene and acetylene molecules. For this, we will look at their molecular structure and observe the number of shared electron pairs between carbon atoms. Ethylene (C2H4) has a double bond (consisting of two pairs of shared electrons) between the carbon atoms, which is represented by two parallel lines. On the other hand, acetylene (C2H2) has a triple bond (consisting of three pairs of shared electrons) between the carbon atoms, represented by three parallel lines.

Compare the bond strengths

Now that we have identified the type of bond in both molecules, we can compare their bond strengths. In general, single bonds are the weakest, followed by double bonds, and triple bonds are the strongest. This is because more shared electrons in a bond result in a stronger electrostatic attraction between the atoms involved in the bond. Since ethylene (C2H4) has a double bond and acetylene (C2H2) has a triple bond between the carbon atoms, we can conclude that the bond in acetylene (C2H2) is stronger than the bond in ethylene (C2H4).

Explain the result

The stronger bond in acetylene (C2H2) can be explained by the greater number of shared electron pairs between the carbon atoms. With three pairs of shared electrons, the electrostatic attraction between the carbon atoms in acetylene is stronger compared to the two pairs of shared electrons in ethylene. The greater the bond strength, the more energy required to break the bond.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Ethylene Molecular Structure

Understanding the structure of ethylene, or C₂H₄, is crucial to grasp why its carbon-to-carbon bond has the characteristics it exhibits. In ethylene, each carbon atom forms what is known as a double bond with the other carbon atom. This bonding involves two pairs of electrons being shared between the carbon atoms. Imagine sharing a handshake with someone using both hands – that represents the double bond situation in ethylene.

Role of Hybridization

In terms of orbital hybridization, each carbon in ethylene undergoes sp² hybridization, which results in the formation of a planar molecule with bond angles of approximately 120 degrees. This structural formation is key to both the chemical reactivity and bond strength of ethylene. The sharing of two pairs of electrons provides considerable bond strength, but not as much as bonds that share more pairs.

Visualize ethylene’s molecular layout with its carbon atoms at the center of a V-shaped formation, with hydrogen atoms at the tips – each angle is a testament to the sp² hybridization and affects how this molecule interacts in reactions and in forming new bonds.

Acetylene Molecular Structure

Acetylene, or C₂H₂, presents a different scenario of bonding between carbon atoms when compared to ethylene. Acetylene's carbon atoms are connected by a triple bond, signifying the sharing of three pairs of electrons. Similar to a trio of parallel lines, the triple bond denotes a powerful pact between the two carbon atoms, much stronger than a single or double bond.

Implications of Linear Configuration

The molecular structure of acetylene is linear due to sp hybridization in its carbon atoms. This arrangement fosters a bond angle of 180 degrees between the hydrogen-carbon bonds. The linear structure culminates in a molecule with immense rigidity and significant bond strength, which is instrumental in its chemical behavior and bonding resilience.

When picturing acetylene, think of a straight line with the carbon atoms in the middle and the hydrogen atoms on the ends, exemplifying the linear and tight-knit configuration enforced by the triple bonding and sp hybridization.

Electron Sharing in Bonds

The concept of electron sharing in bonds is fundamental to understanding chemical bond strength. When atoms bond, they share electrons to attain stability – similar to friends sharing resources to ensure everyone has what they need. In the realm of carbon atoms within hydrocarbons, the extent of sharing determines the might of their bond.

Double Bonds vs. Triple Bonds

In a double bond, two pairs of electrons are shared between atoms; in ethylene this creates a certain level of stability and strength. However, a triple bond, like in acetylene, ups the ante by sharing three pairs of electrons, resulting in an enhanced electrostatic attraction between the atoms. It’s akin to the difference between a strong magnet (triple bond) and a weaker one (double bond).

The more electron pairs involved in the bond, the tighter the electrons hold the nuclei together, leading to a more robust bond. This electron sharing dance is key to understanding why different types of bonds offer varying levels of strength and reactivity.

Bond Strength Comparison

Bond strength comparison between ethylene and acetylene becomes intuitive when considering the number of shared electron pairs. Recall that the triple bond in acetylene consists of one more pair of shared electrons than the double bond in ethylene. This additional pair means acetylene’s carbon-carbon bond grips with a firmer handshake than that of ethylene.

The Energy Perspective

From an energy standpoint, breaking acetylene's bond would necessitate a heftier input of energy compared to separating the double-bonded carbons in ethylene. It’s a reflection of the existential truth – the more robust the connection, the greater the effort required to break it.

To summarize, one can think of acetylene as a stronger adhesive when compared to ethylene, all because of that one extra pair of electrons holding things together in a tighter embrace. This understanding is not only foundational for grasping chemical bond strengths but also for anticipating the behavior of these molecules during chemical reactions.

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Is the bond between the carbon atoms in the ethylene molecule of Problem \(5.84\) stronger or weaker than the bond in acetylene, \(\mathrm{C}_{2} \mathrm{H}_{2}\) (WorkPatch 5.7)? Explain fully.

Short Answer

Step by step solution

Identify the type of bonds in each molecule

Compare the bond strengths

Explain the result

Key Concepts

Ethylene Molecular Structure

Role of Hybridization

Acetylene Molecular Structure

Implications of Linear Configuration

Electron Sharing in Bonds

Double Bonds vs. Triple Bonds

Bond Strength Comparison

The Energy Perspective

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