Question

The oxidation states of S-atoms in Caro's and Marshell's acids are: (a) \(+6,+6\) (b) \(+6+4\) (c) \(+6,-6\) (d) \(+4,+6\)

Short answer

(a) +6,+6

Step-by-step solution

Identify Caro's Acid

Caro's acid, also known as peroxymonosulfuric acid, has the chemical formula H2SO5. The sulfur (S) atom is bonded to an additional oxygen atom through a peroxy bond. The structure can be written as H2SO4 with an extra '-OOH' group.

Assign Oxidation States in Caro's Acid

Considering the structure of H2SO5, the oxidation state of S can be determined by summing up the states of individual atoms and setting it equal to the overall charge, which is zero for a neutral molecule. For oxygen in a peroxy linkage, its oxidation state is -1, otherwise it is -2. Hydrogen is always +1. Therefore, in Caro's acid, S has an oxidation state of +6.

Identify Marshall's Acid

Marshall's acid, also known as peroxodisulfuric acid, has the chemical formula H2S2O8. It consists of two S atoms interconnected with a peroxy link.

Assign Oxidation States in Marshall's Acid

In Marshall's acid (H2S2O8), like Caro's acid, the peroxy oxygen atoms are assigned an oxidation state of -1. The other oxygen atoms have -2. Hydrogen atoms have +1. The S atoms in H2S2O8 are in a symmetrical arrangement, meaning both have the same oxidation state. Summing up the oxidation states should equal zero since it's a neutral molecule. Therefore, each S atom in Marshall's acid also has an oxidation state of +6.

Collect The Results

Based on the oxidation state assignments, the S-atoms in Caro's and Marshall's acids both have oxidation states of +6. Therefore, the correct answer is (a) +6,+6.

Key concepts

Caro's acid

Caro's acid, commonly known as peroxymonosulfuric acid, plays a key role in oxidation reactions in organic and inorganic chemistry. With its chemical formula of H2SO5, it's understood that the molecule is composed of hydrogen (H), sulfur (S), and oxygen (O) atoms. A distinct feature of Caro's acid is the presence of a peroxy bond, which links an additional oxygen atom to the sulfur.

The peroxy linkage impacts the oxidation state of the involved atoms, notably assigning the oxygen in the -OOH group an oxidation state of -1. This differs from the standard -2 oxidation state typical for oxygen because the peroxy bond's characteristics alter the electron distribution between the oxygen atoms. This distinction is crucial when analyzing Caro's acid for redox processes or synthesizing organic compounds. Simplifying the structure, Caro's acid can be visualized as a traditional sulfate molecule (H2SO4) with an extra '-OOH' group attached.

Marshall's acid

Marshall's acid, which is also referred to as peroxodisulfuric acid, is another powerful oxidizing agent that is represented by the formula H2S2O8. This molecule is similar to Caro's acid in that it integrates peroxy bonds within its structure; however, Marshall's acid contains two sulfur atoms instead of one. The duplicate sulfur atoms are each part of their own sulfate-like units and are connected by a peroxy linkage.

The presence of this bond has pivotal consequences for the oxidation state of the constituent oxygens, assigning those within the peroxy linkage an oxidation state of -1. On the other hand, the remaining oxygen atoms retain the more common oxidation state of -2. The hydrogen atoms, as with Caro's acid, sustain an oxidation state of +1. The symmetrical arrangement of the sulfur atoms within Marshall's acid implies that they share identical oxidation states, thus simplifying the process of determining their respective oxidation numbers.

Peroxymonosulfuric acid

Peroxymonosulfuric acid, known under its more common name Caro's acid, is widely utilized in chemical applications, particularly for its strong oxidizing properties. Its molecular composition includes a single sulfur atom bonded to multiple oxygen atoms. In organic chemistry, peroxymonosulfuric acid is employed for converting alkenes through oxidation to epoxides, which are valuable intermediates for further chemical transformations.

Understanding the behavior of Caro's acid requires knowledge of its oxidation state, which influences the acid's reactivity. Clarifying the oxidation state involves recognizing the unique status of the peroxy oxygen atom, which departs from general rules due to its bonding configuration. This specific characteristic influences how Caro's acid interacts with other chemical species and contributes to the potential it holds as a strong oxidizing agent.

Peroxodisulfuric acid

Peroxodisulfuric acid, also known as Marshall's acid, showcases a dimeric arrangement with its formula H2S2O8, signifying two sulfuric units joined by a peroxy bond. It's extensively applied in industrial settings, such as the cleaning of semiconductor surfaces and as an etching agent. The peroxy linkage in the acid not only influences its structural integrity but also the oxidation states of the atoms involved.

Unlike monomeric Caro's acid, the peroxide bond in Marshall's acid unites two sulfur atoms, still endowing the linkage's oxygen atoms with an atypical oxidation state of -1. When addressing redox chemistry involving Marshall's acid, these non-standard oxidation states can play a substantial role in the compound's reactivity and efficacy as an agent in oxidative reactions.

Assigning oxidation numbers

The determination of oxidation numbers, or states, is integral to understanding redox reactions in chemistry. Oxidation numbers serve as a tool for figuring out how electrons are distributed in a molecule and are pivotal in identifying changes that occur during chemical reactions. They are assigned to atoms in a molecule based on a set of rules which take into account the molecular structure and the nature of the chemical bonds.

For instance, hydrogen is typically assigned an oxidation number of +1, and oxygen is usually -2 except in peroxides like Caro's and Marshall's acids, where it is -1. Various structural features, such as peroxy linkages, require special consideration when assigning these numbers. The overall charge of a neutral molecule must sum to zero, and it is this concept that underpins the process of assigning accurate oxidation states. Understanding how to assign oxidation numbers is essential for anyone studying redox chemistry, predicting reaction outcomes, and balancing chemical equations.