Question

Is there a difference between a homogeneous mixture of hydrogen and oxygen in a 2:1 mole ratio and a sample of water vapor? Explain.

Short answer

Yes, there is a difference between a homogeneous mixture of hydrogen and oxygen in a 2:1 mole ratio and a sample of water vapor. The homogeneous mixture consists of separate hydrogen and oxygen gas molecules, whereas water vapor is made up of water molecules, which are a result of a chemical reaction between hydrogen and oxygen. Additionally, the homogeneous mixture can be reactive and potentially explosive, while water vapor is relatively stable.

Step-by-step solution

Understand the homogeneous mixture of hydrogen and oxygen gases

In a homogeneous mixture, the components are evenly distributed throughout the mixture. In this case, we have a mixture of hydrogen and oxygen gases in a 2:1 mole ratio. This means that for every two moles of hydrogen gas, there is one mole of oxygen gas. However, the two gases are separate entities - they have not combined or reacted with one another to form any new substance.

Understand sample of water vapor

Water vapor is the gaseous phase of water (H2O). It is formed when water molecules absorb enough energy to overcome the forces holding them together in the liquid or solid phase, thus transitioning into the gas phase. Water vapor is a pure substance, with individual water molecules consisting of two hydrogen atoms bonded to one oxygen atom. It is not a mixture of separate hydrogen and oxygen gas molecules.

Comparing the homogeneous mixture and water vapor

Now that we have a basic understanding of both the homogeneous mixture of hydrogen and oxygen gases and water vapor, we can compare the two. The significant difference between the two lies in the fact that the homogeneous mixture consists of separate hydrogen and oxygen gas molecules, while water vapor consists of individual water molecules made up of hydrogen and oxygen atoms. In simple terms, the homogeneous mixture is just a mixture of individual gases, whereas water vapor is the result of a chemical reaction between hydrogen and oxygen.

Chemical reactivity difference

Another significant difference is their reactivity and behavior under certain conditions. The homogeneous mixture of hydrogen and oxygen in a 2:1 mole ratio can be very reactive and potentially explosive if exposed to a flame or spark, as it can form water through a chemical reaction (2H2(g) + O2(g) -> 2H2O(g)). On the other hand, water vapor (H2O) is relatively stable, as it already exists as a result of a chemical reaction between hydrogen and oxygen, and it would only decompose into its elements under extremely high temperatures or energy conditions. In conclusion, there is indeed a difference between a homogeneous mixture of hydrogen and oxygen in a 2:1 mole ratio and a sample of water vapor. The homogeneous mixture is composed of individual hydrogen and oxygen gas molecules, while water vapor is composed of water molecules, resulting from the chemical reaction between hydrogen and oxygen. Furthermore, the reactivity of these two systems is quite different.

Key concepts

Understanding Homogeneous Mixtures

A homogeneous mixture is characterized by a uniform composition throughout its substance. In the case of a mixture of hydrogen and oxygen in a 2:1 mole ratio, it means the different molecules are distributed evenly throughout the mixture. However, these molecules do not react or bond with each other; they simply coexist in the same space. This makes them distinct from compounds or substances resulting from chemical reactions, where new chemical bonds are formed. Homogeneous mixtures of gases have particles that remain separate and intact, each retaining its original properties. They can be mixed and yet still measured individually, contributing to the properties of the mixture without altering their own identities. This concept is crucial when discussing mixtures as it helps us understand the differences between physical mixtures and chemical compounds.

It's important to remember that while the gases in a homogeneous mixture can remain stable under normal conditions, they might react when exposed to certain triggers, such as a spark or flame.

The Nature of Water Vapor

Water vapor is a fascinating phase of water that occurs when water molecules absorb enough energy to transition from liquid or solid to gas. In its gaseous state, water vapor consists purely of water molecules, signifying that a chemical bonding has occurred between hydrogen and oxygen atoms to form the compound H2O. Each water molecule is made up of two hydrogen atoms covalently bonded to one oxygen atom, creating a stable structure. This transformation from liquid or solid involves breaking intermolecular attractions or forces within water, which requires energy.

Though in a gaseous form, water vapor is not a mixture of hydrogen and oxygen gases; it doesn't separate into its elemental components without significant energy, such as extreme heat. It is the result of a chemical reaction, distinct from a simple mixture, and stands as a pure substance due to the consistent presence of bonded, intact water molecules.

Understanding Gas Molecular Behavior

The behavior of gas molecules in mixtures and compounds such as homogeneous mixtures of hydrogen and oxygen and water vapor can be quite different. Gas molecules in a homogeneous mixture exhibit random motion and equal distribution across the available volume they occupy. This characteristic allows for even mixing and is a result of the kinetic energy that gas molecules inherently possess. These molecules collide and move freely, without forming new substances.

In contrast, within water vapor, the gas molecules are water molecules themselves. These molecules are held together by covalent bonds, exhibiting different properties than a mere mixture. These water molecules, in the gas phase, still exhibit the typical behavior of gases like spreading out to fill the available space and having a fluid form. Even though they exhibit some similar behaviors to those in mixtures, their chemical stability and identity as H2O molecules differentiate them significantly, showcasing a chemical bond unlike the mere physical presence in mixtures.