Problem 20 - General Chemistry

Question

Write the chemical equation for the formation reaction of \(\mathrm{H}_{2} \mathrm{~S}(g)\).

Step-by-Step Solution

Answer

The formation reaction is \( \text{H}_2(g) + \frac{1}{8}\text{S}_8(s) \rightarrow \text{H}_2\text{S}(g) \).

Step 1: Understand the Chemical Components

In this formation reaction, we need to produce hydrogen sulfide gas, which is represented by the chemical formula \( \text{H}_2\text{S}(g) \). This involves hydrogen (\( \text{H} \)) and sulfur (\( \text{S} \)) as the reactants.

Step 2: Identify the States of Each Element

In a formation reaction, elements must be in their standard states. Here, hydrogen is a diatomic molecule \( \text{H}_2(g) \) in its gaseous state and sulfur is usually found as solid sulfur, \( \text{S}_8(s) \).

Step 3: Write the Formation Reaction

For the formation of \( \text{H}_2\text{S}(g) \), hydrogen gas and sulfur solid react to form hydrogen sulfide gas. The chemical equation can be written as: \[ \text{H}_2(g) + \frac{1}{8}\text{S}_8(s) \rightarrow \text{H}_2\text{S}(g) \]

Step 4: Balance the Chemical Equation

The equation is already balanced in terms of hydrogen. For sulfur, adjust it to produce the desired compound. Hence, the complete balanced equation is: \[ \text{H}_2(g) + \frac{1}{8}\text{S}_8(s) \rightarrow \text{H}_2\text{S}(g) \]

Key Concepts

Formation Reaction

A formation reaction is a type of chemical reaction where one mole of a compound is formed from its constituent elements in their standard states. This means that the starting materials, or reactants, are the pure elements that make up the compound. Understanding this concept is key to writing correct chemical equations for these types of reactions. In the case of hydrogen sulfide (\(\text{H}_2\text{S}(g)\)), we begin with hydrogen and sulfur. Because these elements must be in their standard states, hydrogen is present as diatomic hydrogen gas \(\text{H}_2(g)\), and sulfur is in its elemental form \(\text{S}_8(s)\), which is the most stable form of sulfur at room temperature.

Hydrogen Sulfide

Hydrogen sulfide is a chemical compound with the formula \(\text{H}_2\text{S}\). It is a colorless gas well-known for its distinctive smell of rotten eggs. This simple binary chemical compound is composed of two hydrogen atoms bonded to a single sulfur atom. While it occurs naturally in crude petroleum, natural gas, and hot springs, it is also produced by the bacterial breakdown of organic matter in the absence of oxygen.

Here are some key points about hydrogen sulfide:

• It is denser than air, which means it can accumulate in low-lying areas.
• It is flammable and can cause irritation to the eyes, nose, and throat.
• Despite its toxicity at higher concentrations, humans can detect it at very low concentrations due to its strong odor.

Balancing Chemical Equations

Balancing chemical equations involves ensuring equal numbers of each type of atom on both sides of the equation. This reflects the conservation of mass, meaning that matter cannot be created or destroyed in a chemical reaction. When writing a balanced chemical equation for the formation of hydrogen sulfide, we start with the unbalanced equation:\[\text{H}_2(g) + \text{S}_8(s) \rightarrow \text{H}_2\text{S}(g)\]

To balance this, we need to make the number of each type of atom the same on both sides. Since sulfur exists naturally as \(\text{S}_8\), we adapt the equation by using \(\frac{1}{8}\text{S}_8\), balancing the sulfur atoms. Thus, the fully balanced equation is:\[\text{H}_2(g) + \frac{1}{8}\text{S}_8(s) \rightarrow \text{H}_2\text{S}(g)\]

Balancing chemical equations is essential not only for correctly representing chemical reactions but also for calculating the amounts of reactants and products involved in reactions.