Problem 67 - Chemistry Matter and Change

Question

Hydrogen iodide gas breaks down into hydrogen gas and iodine gas during a decomposition reaction. Write a skeleton equation for this reaction.

Step-by-Step Solution

Answer

The skeleton equation is: \( \text{HI} \rightarrow \text{H}_2 + \text{I}_2 \).

Step 1: Identify the Reactant

The reactant in the decomposition reaction is hydrogen iodide. It is given in the problem statement. Hydrogen iodide is a compound made from hydrogen (H) and iodine (I), and its chemical formula is HI.

Step 2: Identify the Products

In the decomposition of hydrogen iodide, the products are hydrogen gas and iodine gas. Hydrogen gas has the chemical formula H₂ and is diatomic, meaning two hydrogen atoms are bonded together. Iodine gas also forms a diatomic molecule, with the formula I₂.

Step 3: Write the Skeleton Equation

A skeleton equation shows the formulas of all reactants and products but does not indicate their amounts (i.e., it's not balanced). For the decomposition of hydrogen iodide, the reactant is HI and the products are H₂ and I₂. Therefore, the skeleton equation is: \[ ext{HI} ightarrow ext{H}_2 + ext{I}_2 \]

Key Concepts

Understanding Hydrogen Iodide

Hydrogen iodide is a compound made from the combination of hydrogen and iodine atoms. It is represented by the chemical formula HI. In this compound, one hydrogen (H) atom is bonded to one iodine (I) atom. Hydrogen iodide is known for being a strong acid when dissolved in water, forming hydroiodic acid. It behaves as a simple binary acid consisting only of hydrogen and iodine. This compound plays a critical role in various chemical reactions, including decomposition reactions, where it breaks down into different substances.

What is a Chemical Equation?

A chemical equation is a written representation that uses chemical formulas to depict what happens during a chemical reaction. It indicates which substances, known as reactants, are consumed and which substances, known as products, are formed. Chemical equations symbolize the transformation of matter in a reaction. For instance, in the decomposition of hydrogen iodide, the chemical equation shows hydrogen iodide (HI) as the reactant breaking down into hydrogen gas (H₂) and iodine gas (I₂) as the products. A skeleton equation only shows the basic formulas of the reactants and products without balancing the moles of each element involved.

Understanding Reactants and Products

In a chemical reaction, the initial substances that undergo change are called reactants, while the substances that are produced as a result of the reaction are called products. During the decomposition of hydrogen iodide, the reactant is HI. This compound breaks down to form two products: hydrogen gas (H₂) and iodine gas (I₂).

Here's a breakdown of these roles:

• Reactant: Hydrogen iodide (HI), which decomposes in the reaction.
• Products:
  • Hydrogen gas (H₂) - a diatomic molecule consisting of two hydrogen atoms bonded together.
  • Iodine gas (I₂) - a diatomic molecule consisting of two iodine atoms bonded together.

Understanding the role of reactants and products is essential for analyzing any chemical reaction.

Diatomic Molecules: Basics

Diatomic molecules are molecules composed of only two atoms, which may be either of the same or different chemical elements. In our specific reaction involving hydrogen iodide, both the products, hydrogen gas (H₂) and iodine gas (I₂), are diatomic molecules.

These molecules are stable in their diatomic form because the atoms share electrons to achieve a more stable electronic arrangement.

• Hydrogen gas (H₂): Consists of two hydrogen atoms. It is a colorless and highly flammable gas.
• Iodine gas (I₂): Consists of two iodine atoms. It is a violet-colored gas that sublimates easily under certain conditions.

Diatomic molecules are crucial to understanding the nature of certain elements in their natural gaseous state.