Question

You have two colorless gases, each made of sulfur and oxygen. If they have different percent compositions, can they be the same substance?

Short answer

Yes, the two gases each made of sulfur and oxygen can be different substances if they have different percent compositions. This leads to different characteristics, properties and behavior of the substances, despite having the same constituting elements.

Step-by-step solution

- Understanding Basic Principle

In chemistry, the percent composition is the percentage by mass of each element in a compound. The type of the compound does not depend only on its elements, but also how these elements are bonded including their ratios.

- Identify Substances from Same Elements

Knowing the principle mentioned earlier, it is clear that even if we have the same elements like sulfur and oxygen, we can still have different substances depending on the ratio and bonding of the elements. Examples for this can be Sulfur Dioxide \((SO_{2})\) or Sulfur Trioxide \((SO_{3})\), both consisting of sulfur and oxygen but in a different ratio, hence they are different substances.

- Concluding

Thus, acknowledging the importance of the ratio of combination, it's clear that two gases each made of sulfur and oxygen can be different substances despite having the same elements. This is due to their different percent compositions, meaning that the elements are combined in a different ratio, resulting in different chemical and physical properties.

Key concepts

Chemical Compounds

Chemical compounds are substances composed of two or more different types of atoms that are bonded together in a fixed proportion. These compounds can be broken down into simpler substances by chemical means. They have unique properties that differ from the elements they are made of, and these properties are determined by the type of atoms involved, the way those atoms are bonded, and the ratio of different atoms.

For example, table salt is a compound made from sodium and chlorine in a 1:1 ratio, known as sodium chloride (NaCl), while water is formed from hydrogen and oxygen in a 2:1 ratio, known as H₂O. Understanding the composition of chemical compounds is crucial in the field of chemistry as it impacts everything from the compound's reactivity to its physical characteristics.

Elemental Ratios

An elemental ratio is a fundamental concept in chemistry that refers to the proportion of one element to another within a compound. This ratio is often expressed in terms of moles, which is a standard unit in chemistry for measuring the amount of a substance. It determines the molecular formula of the compound, which in turn can provide insights into its structure and properties.

To determine the elemental ratio, you would typically divide the number of moles of one element by the number of moles of another. For instance, in carbon dioxide (CO₂), there are two oxygen atoms for every one carbon atom, which gives an elemental ratio of 2:1 for oxygen to carbon. Elemental ratios are integral to understanding the percent composition of compounds, as they directly affect the mass percentage of each element.

Sulfur Dioxide (SO2)

Sulfur dioxide (SO₂) is a colorless gas with a pungent, suffocating odor. It is a compound composed of one sulfur atom and two oxygen atoms. This makes it an example of a sulfur oxide, which is a family of compounds featuring combinations of sulfur with oxygen.

SO₂ plays a crucial role in both the environment and industry. It is produced naturally by volcanic activity and is also a by-product of burning fossil fuels. In the atmosphere, SO₂ can lead to acid rain formation when it reacts with water vapor. In industry, it is used in the production of sulfuric acid, which is a vital chemical for numerous applications. The percent composition by mass in sulfur dioxide for sulfur is approximately 50.0%, and for oxygen is about 50.0% as well, reflecting the molecular weight and the number of atoms of each element.

Sulfur Trioxide (SO3)

Sulfur trioxide (SO₃) is yet another sulfur oxide, this time with a composition of one sulfur atom to three oxygen atoms. Unlike sulfur dioxide, it exists in several forms, including a gas, liquid, or solid. It does not have a smell in its pure state and forms a dense white vapor when exposed to air.

SO₃ is pivotal in industrial chemistry, especially in the production of sulfuric acid through the contact process. The percent composition by mass in sulfur trioxide for sulfur is roughly 40.0%, while for oxygen, it is about 60.0%. This difference in percent composition compared to sulfur dioxide reflects the added oxygen atom and shows how additional atoms affect the overall weight and properties of a compound, resulting in distinct substances even with the same elements involved.