Problem 44 - Chemistry Matter and Change

Question

What is the oxidation number of manganese in KMnO \(_{4} ?\)

Step-by-Step Solution

Answer

The oxidation number of manganese (Mn) in KMnO\(_{4}\) is +7.

Step 1: Identify the elements and their known oxidation numbers

In KMnO\(_{4}\), we have potassium (K), manganese (Mn), and oxygen (O). The oxidation number of potassium (K) is always +1. The oxidation number of oxygen (O) in compounds is usually -2, except in peroxides, where it is -1. Since this is not a peroxide, we can assume the oxidation number of oxygen (O) is -2.

Step 2: Set up the equation using the sum of oxidation numbers

As mentioned earlier, in a neutral compound, the sum of oxidation numbers of all the elements is equal to 0. Let's denote the oxidation number of manganese (Mn) as x. So we can set up the equation as: \[ (+1) + x + 4(-2) = 0 \]

Step 3: Solve the equation to find the oxidation number of manganese (Mn)

Now, we will solve the equation for x: \[ +1 + x - 8 = 0 \] \[ x - 7 = 0 \] \[ x = 7 \] Thus, the oxidation number of manganese (Mn) in KMnO\(_{4}\) is +7.

Key Concepts

Manganese Oxidation State

Understanding the oxidation state of manganese is crucial in chemistry, especially when dealing with redox reactions. Manganese is a transitional metal known for having multiple oxidation states ranging from +2 to +7. In the compound potassium permanganate (KMnO\(_{4}\)), manganese exhibits an oxidation state of +7. This is its highest oxidation state and is common when manganese is part of compounds where oxygen atoms are involved. To find the oxidation state of manganese in a compound, you can use the known oxidation states of other elements and the overall charge of the compound. For KMnO\(_{4}\), potassium (K) has a +1 oxidation state and oxygen (O) has a -2 oxidation state. Thus, in this neutral compound, the oxidation state of manganese must balance the charges contributed by the other elements, leading to manganese having an oxidation state of +7.

Chemical Compounds

Chemical compounds are substances formed by the chemical combination of two or more elements. The compound potassium permanganate (KMnO\(_{4}\)) is made up of potassium, manganese, and oxygen atoms. These elements come together in specific ratios to form a stable compound.In KMnO\(_{4}\):

• Potassium (K) typically forms ionic bonds, contributing a +1 charge.
• Manganese (Mn) can form various oxidation states, but in KMnO\(_{4}\), it reaches the +7 state, making it a potent oxidizing agent.
• Oxygen (O) generally forms two bonds or gains two electrons, presenting a -2 oxidation state in most compounds.

All these properties combine to create the oxidizing power and stability of potassium permanganate, making it widely used in chemical reactions and various industrial applications.

Redox Chemistry

Redox chemistry involves the study of reduction and oxidation reactions. These reactions involve the transfer of electrons between substances. In a redox reaction, one substance is oxidized (loses electrons) and another is reduced (gains electrons).When understanding redox chemistry, it's important to note:

• The oxidation number indicates the degree of oxidation (or reduction) of an element in a compound.
• An increase in oxidation number occurs during oxidation, while a decrease indicates reduction.
• Potassium permanganate (KMnO\(_{4}\)) is a classic example of an oxidizing agent. Manganese in KMnO\(_{4}\) often undergoes a reduction from the +7 oxidation state to a lower state, such as +2, depending on the reaction.

Such reactions are central to many industrial processes and are critical for biological functions like cellular respiration. Understanding how elements change their oxidation states helps chemists design reactions and understand complex chemical processes.