Question

On the basis of oxidation number considerations, one of the following oxides would not react with molecular oxygen: \(\mathrm{NO}, \mathrm{N}_{2} \mathrm{O}, \mathrm{SO}_{2}, \mathrm{SO}_{3}, \mathrm{P}_{4} \mathrm{O}_{6}\). Which one is it? Why?

Short answer

SO3 is the compound that won't react with molecular Oxygen. This is because Sulphur in SO3 has already reached its maximum oxidation state +6.

Step-by-step solution

Oxidation state of Nitrogen in NO

NO consists of Nitrogen and Oxygen. Oxygen has an oxidation state of -2. As the sum of the oxidation states in a neutrally charged molecule is 0, Nitrogen in NO will have an oxidation state of +2.

Oxidation state of Nitrogen in N2O

N2O is composed of two Nitrogen atoms and one Oxygen atom. As Oxygen has an oxidation number of -2, to balance this and achieve a total oxidation number of 0, each Nitrogen must have an oxidation state of +1.

Oxidation state of Sulphur in SO2 and SO3

Oxygen is present in SO2 and SO3 with oxidation state -2. For SO2, to make the total oxidation number 0, Sulphur will have an oxidation number of +4. For SO3, to balance the total oxidation number to 0, Sulphur needs to have an oxidation state of +6.

Oxidation state of Phosphorus in P4O6

Oxygen in P4O6 has an oxidation state of -2. With 6 Oxygen atoms in the compound, the total negative oxidation charge is -12. To balance this negative charge and make the total oxidation state 0, each Phosphorus in P4O6 must have an oxidation state of +3.

Finding the compound that won't react with oxygen

Since the element Sulphur in SO3 has already reached its maximum oxidation state +6, it will not be able to further react with molecular Oxygen.

Key concepts

chemical reactions

Chemical reactions involve the rearrangement of atoms or molecules to form new substances. During these processes, substances change their chemical properties due to the breaking and forming of bonds. This can result in energy release or absorption. It's crucial to track oxidation numbers in reactions to identify which atoms lose or gain electrons. This gives insight into which elements are oxidized or reduced.

In the context of oxidation states, each element in a compound is assigned a number that represents its ability to gain, lose, or share electrons in a chemical reaction. This helps predict the reactivity of different oxides with molecular oxygen. For instance, if an element is already at its maximum oxidation state in a compound, it is less likely to react further with oxygen, as seen with sulfur in SO₃.

molecular oxygen

Molecular oxygen, denoted as O₂, is a diatomic molecule essential for many chemical reactions, particularly oxidation reactions. It consists of two oxygen atoms sharing a pair of electrons, creating a stable bond. This form of oxygen is commonly found in the atmosphere and is vital for combustion and respiration.

In chemical reactions, molecular oxygen acts as an oxidizing agent, accepting electrons from other elements. This behavior is key when determining which substances will react with it. For oxides like SO₃, where the central element is already at a high oxidation state, further reaction with molecular oxygen becomes improbable because the element cannot accept more electrons without violating its natural state of stability.

sulfur dioxide

Sulfur dioxide (SO₂) is a chemical compound composed of one sulfur atom and two oxygen atoms. It appears as a gas with a sharp, irritating smell. In terms of oxidation state, sulfur in SO₂ has a +4 state. This suggests that sulfur has the potential to be oxidized further in the right conditions.

SO₂ often participates in environmental chemical reactions, forming sulfuric acid in the atmosphere, which can lead to acid rain. Though it can oxidize further when exposed to molecular oxygen, converting to SO₃ (sulfur trioxide), it highlights the compound's reactivity based on oxidation state considerations. Understanding the oxidation states of compounds like SO₂ aids in predicting their chemical behavior and reactivity with elements like molecular oxygen.