Question

Determine the oxidation number for the indicated element in each of the following substances: (a) \(\mathrm{S}\) in \(\mathrm{SO}_{2}\) (b) \(\mathrm{C}\) in \(\mathrm{COCl}_{2},(\mathrm{c}) \mathrm{Mn}\) in \(\mathrm{MnO}_{4}^{-},(\mathrm{d}) \mathrm{Br}\) in \(\mathrm{HBrO},(\mathrm{e}) \mathrm{As}\) in \(\mathrm{As}_{4}\), (f) \(\mathrm{O}\) in \(\mathrm{K}_{2} \mathrm{O}_{2}\).

Short answer

The oxidation numbers for the given substances are as follows: (a) S in SO2: +4, (b) C in COCl2: +4, (c) Mn in MnO4-: +7, (d) Br in HBrO: +1, (e) As in As4: 0, and (f) O in K2O2: -1.

Step-by-step solution

(a) Determine the oxidation number of S in SO2

In SO2, we know that the oxygen's oxidation number is -2. Since SO2 is a neutral compound, the sum of the oxidation numbers has to be zero. Let the oxidation number of Sulfur (S) be x: x + 2(-2) = 0 x - 4 = 0 x = +4 So, the oxidation number of S in SO2 is +4.

(b) Determine the oxidation number of C in COCl2

In COCl2, the oxidation number of O is -2, and of Cl is -1. Let the oxidation number of Carbon (C) be x: x + (-2) + 2(-1) = 0 x - 2 - 2 = 0 x = +4 So, the oxidation number of C in COCl2 is +4.

(c) Determine the oxidation number of Mn in MnO4-

In MnO4-, we know the oxidation number of oxygen is -2. Let the oxidation number of Manganese (Mn) be x: x + 4(-2) = -1 (Since the compound has a charge of -1) x - 8 = -1 x = +7 So, the oxidation number of Mn in MnO4- is +7.

(d) Determine the oxidation number of Br in HBrO

In HBrO, we know the oxidation number of H is +1, and O is -2. Let the oxidation number of Bromine (Br) be x: 1 + x + (-2) = 0 x - 1 = 0 x = +1 So, the oxidation number of Br in HBrO is +1.

(e) Determine the oxidation number of As in As4

Since As4 is an elemental form of Arsenic, the oxidation number is 0.

(f) Determine the oxidation number of O in K2O2

In K2O2, we know the oxidation number of K is +1. Let the oxidation number of Oxygen (O) be x: 2(+1) + 2(x) = 0 2 + 2x = 0 2x = -2 x = -1 So, the oxidation number of O in K2O2 is -1.

Key concepts

Redox Reactions

Redox reactions are chemical processes where the oxidation states of elements change. These reactions consist of two key parts: oxidation, where an element loses electrons, and reduction, where an element gains electrons.
Redox reactions play an essential role in energy conversion, corrosion, and more. To understand these reactions, identifying the change in oxidation numbers is crucial:

• Identify which element is oxidized (loses electrons) and which is reduced (gains electrons).
• Track the movement of electrons to understand the reaction fully.
• Use oxidation numbers to determine which elements are undergoing oxidation or reduction.

Understanding redox reactions helps us in a wide range of chemical applications, from batteries to biological processes.

Oxidation States

Oxidation states, also known as oxidation numbers, are used to keep track of electron transfer in redox reactions. The oxidation state is a hypothetical charge an atom would have if all bonds to it were completely ionic. Knowing these helps scientists understand how electrons flow in a reaction.

• Oxidation states are assigned to each atom in a molecule or compound.
• The sum of the oxidation states must equal the overall charge of the molecule or ion.
• Common oxidation states for oxygen is -2, and for hydrogen is +1.

By understanding oxidation states, you can analyze complex chemical reactions and predict products.

Chemical Compounds

Chemical compounds are substances formed by two or more different elements bonded together. They have unique properties different from the individual elements that make them up.
Classifying compounds and understanding their structure is key to predicting their behavior in reactions:

• Covalent compounds involve sharing electron pairs between atoms.
• Ionic compounds result from the transfer of electrons, forming charged ions.
• Compounds can be neutral or charged, affecting how they react chemically.

Understanding the composition of chemical compounds helps predict their reactions and properties in various scientific fields.

Elemental Oxidation

Elemental oxidation refers to the process where an element increases its oxidation state by losing electrons during a reaction. This loss of electrons leads to positive oxidation states.
An essential part of understanding elemental oxidation is knowing the initial and final oxidation states:

• An element in its pure form always has an oxidation state of zero.
• Through redox reactions, elements transition to higher or lower oxidation states.
• Recognizing these changes is vital for balancing chemical equations.

The concept of elemental oxidation is foundational when studying energy changes and electron transfer in chemistry.

Neutral Compounds

Neutral compounds have no overall charge. This neutrality means the sum of all individual oxidation numbers must equal zero. Understanding neutral compounds helps predict reaction products and balance equations.

• In a neutral compound, positive and negative oxidation states balance each other.
• Knowing oxidation states helps in predicting molecular behavior.
• Neutral compounds can still take part in redox reactions by altering individual oxidation states.

Analyzing neutral compounds allows scientists to predict products and understand how materials interact in different environments.