Problem 101 - Introductory Chemistry Atoms First

Question

Balance this chemical equation and classify it as combination, decomposition, single-replacement, or double-replacement: \(\mathrm{K}_{2} \mathrm{SO}_{3}+\mathrm{S}_{8} \rightarrow \mathrm{K}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}\)

Step-by-Step Solution

Answer

The balanced chemical equation is: \(\mathrm{4K}_{2} \mathrm{SO}_{3} + 3\mathrm{S}_{8} \rightarrow 8\mathrm{K}_{2} \mathrm{S}_{2} \mathrm{O}_{3}\). The reaction is classified as a redox reaction.

Step 1: Identify reactants and products

First, let's identify the reactants and products in the given equation: Reactants: \(\mathrm{K}_{2} \mathrm{SO}_{3}\) (potassium sulfite) and \(\mathrm{S}_{8}\) (sulfur) Products: \(\mathrm{K}_{2} \mathrm{S}_{2} \mathrm{O}_{3}\) (potassium thiosulfate)

Step 2: Balance the equation

Next, we need to balance the equation by making sure the number of atoms of each element is the same on both sides of the equation. The original equation: \(\mathrm{K}_{2} \mathrm{SO}_{3} + \mathrm{S}_{8} \rightarrow \mathrm{K}_{2} \mathrm{S}_{2} \mathrm{O}_{3}\) Balanced equation (with coefficients for the reactants and products): \(\mathrm{4K}_{2} \mathrm{SO}_{3} + 3\mathrm{S}_{8} \rightarrow 8\mathrm{K}_{2} \mathrm{S}_{2} \mathrm{O}_{3}\) On both sides of the equation, we now have 8 potassium atoms, 24 sulfur atoms, and 12 oxygen atoms.

Step 3: Classify the reaction

Finally, we will classify the reaction according to the four possible types: combination, decomposition, single-replacement, or double-replacement. Combination: Two or more reactants combine to form a single product. This does not apply, as there are multiple products. Decomposition: A single reactant breaks apart into two or more products. This does not apply, as there are multiple reactants. Single-replacement: One element replaces another element in a compound. This does not apply, as no single element is being replaced. Double-replacement: The positive and negative ions in two ionic compounds exchange places. This does not apply, as there is only one ionic compound involved. None of the above categories perfectly fit our reaction, so this reaction is best described as a redox reaction (reduction-oxidation) where the oxidation state of sulfur in potassium sulfite is changing due to the gain of more sulfur atoms. The balanced chemical equation is: \(\mathrm{4K}_{2} \mathrm{SO}_{3} + 3\mathrm{S}_{8} \rightarrow 8\mathrm{K}_{2} \mathrm{S}_{2} \mathrm{O}_{3}\) The reaction is classified as a redox reaction.

Key Concepts

reaction classification

Understanding how to classify chemical reactions is essential for recognizing the type and nature of changes occurring within a reaction. In general, reactions can be classified into four main types: combination, decomposition, single-replacement, and double-replacement.

• Combination reactions occur when two or more reactants combine to form a single product.
• Decomposition reactions involve a single reactant breaking apart to yield two or more products.
• Single-replacement reactions occur when one element displaces another in a compound.
• Double-replacement reactions involve the exchange of positive and negative ions between two ionic compounds.

However, it's important to remember that not all reactions fit neatly into these specific categories. Some reactions may involve more complex processes that do not align with these traditional classifications. Such reactions could involve changes like the transfer of electrons, known as redox reactions, which can be overlooked if we rely solely on the basic classifications.

redox reactions

Redox reactions are a fascinating and crucial part of chemical processes, involving the transfer of electrons between substances. The term 'redox' stands for reduction-oxidation:

• Reduction refers to the gain of electrons by a molecule, atom, or ion.
• Oxidation occurs when there is a loss of electrons.

In a redox reaction, one reactant is oxidized, losing electrons, while the other is reduced, gaining those electrons. This electron exchange is what defines a redox reaction. These reactions are prevalent in various natural and industrial processes, including metabolism, combustion, and electrochemical reactions such as in batteries. Understanding the movement of electrons helps in predicting reaction products and energy changes.
In the given balanced equation, \[4\mathrm{K}_{2} \mathrm{SO}_{3} + 3\mathrm{S}_{8} \rightarrow 8\mathrm{K}_{2} \mathrm{S}_{2} \mathrm{O}_{3}\]oxidation and reduction happen to sulfur atoms, indicating a redox process. Recognizing that changes in electron distribution occur can lead to deeper insights into the reaction mechanism.

oxidation state changes

An oxidation state, sometimes called oxidation number, represents the hypothetical charge an atom would have if all bonds were ionic. In redox reactions, the oxidation state of an element changes during the reaction, signifying electron transfer.

• When an atom's oxidation state increases, it is oxidized.
• Conversely, a decrease in oxidation state indicates reduction.

Determining oxidation states helps in identifying which molecules or ions are oxidized or reduced. This is crucial for balancing complex redox equations and understanding the underlying electronic changes occurring in the reaction. In our equation, the alteration of sulfur atoms' oxidation state in potassium sulfite, due to its interaction with elemental sulfur \( \mathrm{S}_8 \), is what classifies the reaction as a redox type.
By analyzing these changes, one gains insights into the redistribution of electrons, which is a central theme in many chemical transformations.