Chapter 9: Problem 17
Compare the structures of \(\mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{H}_{2} \mathrm{O}_{2}\).
Short Answer
Expert verified
Water has a bent structure, while hydrogen peroxide has a trans-planar structure due to an -O-O- bond.
Step by step solution
01
Understand the Basic Components of Each Molecule
Water (\(\text{H}_2\text{O}\)) has two hydrogen atoms and one oxygen atom. Hydrogen peroxide (\(\text{H}_2\text{O}_2\)) has two hydrogen atoms and two oxygen atoms. The primary difference in composition is the additional oxygen in hydrogen peroxide.
02
Investigate the Molecular Geometry of Water
Water is a bent shape molecular geometry. It features a V-shape because of the two lone pairs on the oxygen atom, which create a 104.5-degree angle between the hydrogen atoms. This bent structure is due to the electron pair repulsion according to the VSEPR theory.
03
Investigate the Molecular Geometry of Hydrogen Peroxide
Hydrogen peroxide has an anti-periplanar or trans-planar structure in its most stable form. Each oxygen atom has two lone pairs, and the molecule creates an angle of approximately 94.8 degrees between the two hydrogen atoms bonded across an -O-O- bond. The structure can be seen as two 'bent' paling conjunctions.
04
Compare Electron Pair and Bond Angle Influences
Both molecules have oxygen-hydrogen bonds, but the additional oxygen in hydrogen peroxide adds a -O-O- bond that influences its molecular shape. In water, lone pair repulsion predominantly defines the bent shape. In hydrogen peroxide, both torsional strain from the -O-O- bond and lone pairs come into play, resulting in a distinct bond angle.
05
Determine Overall Molecular Characteristics
Water's structure lends it high polarity, contributing to its solvent properties and high boiling point. Hydrogen peroxide's additional oxygen creates a molecule that is also polar, but with distinct reactivity due to the peroxy linkage, which makes it a strong oxidizing agent. The structural distinctions lead to different physical and chemical behaviors.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
VSEPR theory
Understanding the shapes of molecules is crucial in predicting their chemical properties and behaviors. VSEPR theory, which stands for Valence Shell Electron Pair Repulsion theory, is a fundamental tool used to determine the geometry of a molecule.
It postulates that electron pairs around a central atom will position themselves as far apart as possible. This arrangement reduces repulsion between the pairs, resulting in specific geometric structures. Whether these pairs are part of bonds or are lone pairs (nonbonding), they shape the overall structure.
For example, water (\( \mathrm{H}_{2}\mathrm{O} \)) has a bent shape because of two lone pairs on the oxygen that repel the bonded hydrogen electrons. This leads to a distinctive angle (angle measure to be discussed later), giving water its fascinating properties. The VSEPR theory is key to understanding and predicting molecular shapes of a wide range of compounds from simple diatomic molecules to more complex structures.
It postulates that electron pairs around a central atom will position themselves as far apart as possible. This arrangement reduces repulsion between the pairs, resulting in specific geometric structures. Whether these pairs are part of bonds or are lone pairs (nonbonding), they shape the overall structure.
For example, water (\( \mathrm{H}_{2}\mathrm{O} \)) has a bent shape because of two lone pairs on the oxygen that repel the bonded hydrogen electrons. This leads to a distinctive angle (angle measure to be discussed later), giving water its fascinating properties. The VSEPR theory is key to understanding and predicting molecular shapes of a wide range of compounds from simple diatomic molecules to more complex structures.
Bent molecular geometry
Bent molecular geometry, exemplified by water (\( \text{H}_{2}\text{O} \)), arises when a central atom forms bonds with two atoms and has one or more lone pairs. In water's case, the oxygen atom is at the center, and the molecular shape is bent as a result of the repulsion from the two lone pairs present.
The bonding angle in water is approximately 104.5 degrees. This differs from a linear shape, where the angle would be about 180 degrees without the lone pair influence. These lone pairs make the bonded hydrogen atoms 'bend,' resulting in the well-known angled structure.
In other scenarios like hydrogen peroxide (\( \text{H}_{2}\text{O}_{2} \)), the molecule exhibits bending at each oxygen but with distinct influences such as the -O-O- single bond. The structural formation results in different molecular interactions and characteristics. The bent structure is important as it directly affects the chemical and physical properties, such as boiling points and reactivity.
The bonding angle in water is approximately 104.5 degrees. This differs from a linear shape, where the angle would be about 180 degrees without the lone pair influence. These lone pairs make the bonded hydrogen atoms 'bend,' resulting in the well-known angled structure.
In other scenarios like hydrogen peroxide (\( \text{H}_{2}\text{O}_{2} \)), the molecule exhibits bending at each oxygen but with distinct influences such as the -O-O- single bond. The structural formation results in different molecular interactions and characteristics. The bent structure is important as it directly affects the chemical and physical properties, such as boiling points and reactivity.
Polarity of water
Water is one of the most important molecules on Earth, and its polarity plays a significant role in its unique properties. The bent geometry of water, as described by the VSEPR theory, gives water its polar nature.
Polarity in molecules arises when there is an uneven distribution of electrons. In water, the oxygen atom is more electronegative than the hydrogen atoms, meaning it attracts the shared electrons more strongly. This results in a partial negative charge near the oxygen and a partial positive charge near the hydrogens, creating a dipole moment.
This polarity is crucial for various properties of water, such as its role as a universal solvent, high surface tension, and significant heat capacity. The polar nature allows water molecules to attract each other and dissolve other polar substances, aiding essential biological and chemical processes. Understanding the polarity of water is vital in fields ranging from biology to environmental science.
Polarity in molecules arises when there is an uneven distribution of electrons. In water, the oxygen atom is more electronegative than the hydrogen atoms, meaning it attracts the shared electrons more strongly. This results in a partial negative charge near the oxygen and a partial positive charge near the hydrogens, creating a dipole moment.
This polarity is crucial for various properties of water, such as its role as a universal solvent, high surface tension, and significant heat capacity. The polar nature allows water molecules to attract each other and dissolve other polar substances, aiding essential biological and chemical processes. Understanding the polarity of water is vital in fields ranging from biology to environmental science.
