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Chapter 11: Problem 85

Which of the following pairs are allotropes? (a) oxygen gas \(\left(\mathrm{O}_{2}\right)\) and ozone gas \(\left(\mathrm{O}_{3}\right)\) (b) liquid oxygen \(\left(\mathrm{O}_{2}\right)\) and oxygen gas \(\left(\mathrm{O}_{2}\right)\) (c) amorphous silicon dioxide and quartz (crystalline silicon dioxide)

Short Answer

Expert verified
Only pair (a) represents allotropes: oxygen gas and ozone gas.

Step by step solution

01

Understanding Allotropes

Allotropes are different structural forms of the same element in the same physical state, with distinct physical properties, caused by different atomic arrangements or bonding.
02

Analyzing Pair (a)

In pair (a), the substances are oxygen gas \(\mathrm{O}_{2}\) and ozone gas \(\mathrm{O}_{3}\). Both are different molecular forms of the element oxygen. \(\mathrm{O}_{2}\) and \(\mathrm{O}_{3}\) are allotropes because they exist in the same physical state (gas) with different atomic arrangements.
03

Analyzing Pair (b)

In pair (b), the substances are liquid oxygen \(\mathrm{O}_{2}\) and oxygen gas \(\mathrm{O}_{2}\). Although both have the formula \(\mathrm{O}_{2}\), they are in different physical states (liquid and gas), and thus are not considered allotropes.
04

Analyzing Pair (c)

In pair (c), the substances are amorphous silicon dioxide and quartz (crystalline silicon dioxide). These are forms of silicon dioxide and differ in atomic arrangement (amorphous vs crystalline). However, allotropy typically refers to pure elements, not compounds. Therefore, they are not allotropes.

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Key Concepts

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

Oxygen gas
Oxygen gas, often represented as \(\mathrm{O}_{2}\), is a colorless and odorless gas that is crucial for life on Earth. It makes up about 21% of the Earth's atmosphere and is essential for the process of respiration in many living organisms. This diatomic molecule, meaning it is composed of two oxygen atoms bonded together, plays a vital part in combustion and various biological processes.
  • Oxygen is a key player in cellular respiration, a process that provides energy to cells by breaking down glucose.
  • Its role in combustion means it supports fire, as it reacts with fuels to produce heat and light.
Understanding its molecular structure and importance to both biological and chemical processes is fundamental in chemistry and biology studies. Oxygen gas is an example of one of the allotropes of oxygen.
Ozone
Ozone is another allotrope of oxygen, represented as \(\mathrm{O}_{3}\). Unlike oxygen gas, ozone has a distinct sharp smell and is a bit bluish in color. This triatomic oxygen molecule is crucial for protecting the Earth from harmful ultraviolet (UV) rays.
  • The ozone layer, located in the Earth鈥檚 stratosphere, acts as a shield by absorbing and scattering the solar ultraviolet radiation.
  • At ground level, however, ozone can be a pollutant with harmful effects on respiratory health.
Ozone's different atomic arrangement compared to oxygen gas gives it different properties and functions, showcasing the fascinating concept of allotropes where the same element can exhibit various forms with distinct behaviors.
Atomic arrangement
The atomic arrangement is at the core of understanding allotropes. It refers to how atoms are organized and bonded to each other in a material, which affects its properties. Different arrangements or bonds lead to variations in physical properties like color, hardness, and strength.
  • In the case of oxygen, \(\mathrm{O}_{2}\) and \(\mathrm{O}_{3}\) have vastly different molecular structures affecting their properties.
  • Atomic arrangements are key in distinguishing different allotropes or polymorphs of a substance.
Studying atomic arrangements helps in comprehending how even slight changes in the positioning or number of atoms can lead to entirely different characteristics of a material.
Silicon dioxide
Silicon dioxide, also known as silica, is a compound commonly found in nature as quartz. It has the chemical formula \(\mathrm{SiO}_{2}\) and is widely used in various industries, from glass making to food production.
  • Quartz and other crystalline forms of silicon dioxide are appreciated for their hardness and ability to withstand high temperatures.
  • Amorphous forms lack a definite crystalline structure, making them more flexible.
Although silicon dioxide itself is not an allotrope, its different structural forms, such as quartz versus amorphous silica, illustrate how atomic arrangement can lead to varied material properties. This concept is crucial in materials science as it highlights strain and brittleness differences between amorphous and crystalline forms.
Crystalline structures
Crystalline structures refer to the orderly and repeating arrangement of atoms in a crystalline solid. Such structures are highly organized and can significantly influence the physical properties of the material.
  • Crystalline structures are typically observed in metals and minerals, where the repetitive geometric pattern adds to the material strength.
  • The predictability of the alignment in crystalline solids demonstrates why they tend to be more stable than their amorphous counterparts.
For example, crystalline silicon dioxide (quartz) has atoms arranged in a continuous and uniform pattern, whereas amorphous silicon dioxide has a more random distribution. Understanding these structures aids in the study of material properties and informs countless applications across engineering, technology, and everyday products.

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Most popular questions from this chapter

Explain why the effect of hydrogen bonding on the boiling point is considerably greater for water than for ammonia and hydrogen fluoride. (Hint: The formation of a hydrogen bond requires both a partial positively charged hydrogen atom and unshared pairs of electrons on the electronegative atom.)

Explain why high pressures are needed in the industrial process that makes diamond \(\left(d=3.5 \mathrm{~g} / \mathrm{cm}^{3}\right)\) from graphite \(\left(d=2.2 \mathrm{~g} / \mathrm{cm}^{3}\right)\)

Cesium iodide crystallizes as a simple cubic array of iodide ions with a cesium ion in the center of the cell. The edge of this unit cell is \(445 \mathrm{pm}\) long. Calculate the density of CsI.

Diethyl ether, a substance once used by physicians as a general anesthetic, and \(n\) -butanol both have the molecular formula \(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O} .\) At \(25^{\circ} \mathrm{C},\) the vapor pressure of diethyl ether is 530 torr, and that of \(n\) -butanol is 7.1 torr. (a) Which of these compounds has the stronger intermolecular attractions? (b) Based on the answer to (a), give the relative magnitudes of threc other propertics of these two compounds.

How many atoms of tungsten are present in each unit cell of that metal, if it crystallizes in a body-centered cubic array of atoms?
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