Problem 52 - General Chemistry: Principles and Modern Applications

Question

Indicate the oxidation state of \(S\) in \(\left(\text { a) } \mathrm{SO}_{3}^{2-}\right.\) (b) \(\mathrm{S}_{2} \mathrm{O}_{3}^{2-} ;\) (c) \(\mathrm{S}_{2} \mathrm{O}_{8}^{2-} ;\) (d) \(\mathrm{HSO}_{4}^{-} ;\) (e) \(\mathrm{S}_{4} \mathrm{O}_{6}^{2-}\)

Step-by-Step Solution

Answer

The oxidation states of Sulfur (S) in the compounds are: (a) +4, (b) +2, (c) +7, (d) +6, (e) +2.

Step 1: Understand the rules for Oxidation States

First, it's necessary to know the rules of oxidation states. The oxidation state of a pure element is always zero. The oxidation state of a monoatomic ion is equal to the charge of that ion. Hydrogen usually has an oxidation state of +1 and Oxygen usually has an oxidation state of -2.

Step 2: Calculate the oxidation state for SO3^2-

For SO3^2-, we know the oxidation state of Oxygen(O) is usually -2 and there are 3 of them, so the total oxidation state for O is -6. Since the overall charge of the molecule is -2, the oxidation state of S must be +4 to balance it.

Step 3: Calculate the oxidation state for S2O3^2-

For S2O3^2-, the total oxidation state for 3 Oxygens is -6. To balance the compound with a charge of -2, the total oxidation state for 2 Sulfur atoms must be +4, so the oxidation state for one Sulfur is +2.

Step 4: Calculate the oxidation state for S2O8^2-

For S2O8^2-, the total oxidation state for 8 Oxygens is -16. To balance the compound with a charge of -2, the total oxidation state for 2 Sulfur atoms should be +14, so the oxidation state for one Sulfur is +7.

Step 5: Calculate the oxidation state for HSO4^-

In HSO4^-, the hydrogen and oxygen contribute +1 and -8 respectively to the total oxidation number due to their usual states. The total must equal -1 to balance the compound, which means the oxidation state of S is +6.

Step 6: Calculate the oxidation state for S4O6^2-

In S4O6^2-, the total oxidation state for 6 Oxygens is -12. To balance the compound with a charge of -2, the total oxidation state for 4 Sulfur atoms is +10, so the oxidation state for one Sulfur is +2.

Key Concepts

Sulfur Compounds

Sulfur is a versatile element found in many compounds, each having distinct properties and uses. It is often combined with oxygen to form various anions, which play significant roles in both nature and industrial applications.

Among the common sulfur compounds, sulfites, thiosulfates, and sulfates stand out. Sulfites (\( ext{SO}_3^{2-} \)) are used as preservatives in food, while thiosulfates (\( ext{S}_2 ext{O}_3^{2-} \)) are known for their application in photography as fixing agents. Sulfates (\( ext{HSO}_4^{-} \)) are widespread in nature; they are found in mineral deposits and are used in detergents. Understanding the structural attributes helps in appreciating their role.

Sulfur can exhibit multiple oxidation states, from -2 to +6, allowing it to form a diverse range of compounds. This versatility arises from sulfur's ability to expand its valence shell, accommodating more bonds than the typical octet rule would otherwise allow. Therefore, sulfur compounds are prime examples of elements that defy simple categorization based on oxidation states.

Redox Reactions

Redox reactions, short for reduction-oxidation reactions, are chemical processes in which the oxidation state of atoms changes. These reactions are fundamental in both biological systems and industrial processes. Understanding them is crucial for grasping how energy and materials are transformed.

In a redox reaction, oxidation refers to the loss of electrons, whereas reduction indicates a gain. For example, in the sulfur compounds discussed earlier, identifying the changes in oxidation states helps to determine which species are oxidized and reduced in the reaction. This helps in understanding the electron flow, which is essential for energy conversion, like in batteries or during metabolism in living organisms.

Rules for assigning oxidation states are pivotal for tracking these processes. They provide a systematic way to keep track of electron transfer. For instance, oxygen typically has an oxidation state of -2, while hydrogen is usually +1. According to the original exercise, calculating sulfur’s oxidation state in compounds sheds light on how electron sharing, losing, or gaining occurs. By examining these changes, insights into the reaction mechanisms can be attained.

Chemical Bonding

Chemical bonding is the process by which atoms combine to form molecules. This fundamental concept of chemistry defines how different elements, like sulfur and oxygen, interact and form stable compounds.

There are several types of chemical bonds, with covalent and ionic being the most common. In sulfur compounds, you often observe covalent bonding, where sulfur shares electrons with oxygen. Such sharing helps them achieve a more stable electronic configuration. This is due to the electronegativity differences between sulfur and oxygen, leading to polar covalent bonds that give these molecules distinctive physical and chemical properties.

on the atomic level, sulfur can exhibit bonding in different geometries due to its valence electrons, allowing it to participate in various configurations and vary its oxidation state. This flexibility in bonding forms the basis of many industrial and natural chemical processes. For students, a closer look at these bonds can clarify how molecules are assembled and why certain compounds have unique characteristics.