Question

Magnesium reacts with acids producing hydrogen and corresponding magnesium salts. In sueh reactions, magnesium undergoes (1) Oxidation (2) Reduction (3) Neither oxidation nor reduction (4) Simple dissolution

Short answer

Oxidation

Step-by-step solution

- Understand the Reaction

Magnesium reacts with acids to produce hydrogen gas and magnesium salts. This is a redox (oxidation-reduction) reaction.

- Determine Oxidation State of Magnesium Before Reaction

In its elemental form, magnesium (Mg) has an oxidation state of 0.

- Determine Oxidation State of Magnesium After Reaction

In the reaction with an acid, magnesium forms magnesium salts. For instance, when magnesium reacts with hydrochloric acid (HCl), it forms magnesium chloride (MgCl₂). In MgCl₂, magnesium has an oxidation state of +2.

- Identify Change in Oxidation State

Since magnesium's oxidation state changes from 0 to +2, it loses electrons during the reaction.

- Conclude the Type of Reaction

Losing electrons corresponds to oxidation. Therefore, in this reaction, magnesium undergoes oxidation.

Key concepts

Oxidation States

Oxidation states are used to keep track of electron transfers in chemical reactions. They indicate the degree of oxidation of an atom in a compound. The oxidation state of an element in its pure form is always zero. However, when elements form compounds, their oxidation states change.
For example, pure magnesium (Mg) has an oxidation state of 0 because it is not combined with any other element. When magnesium reacts with hydrochloric acid (HCl) to form magnesium chloride (MgCl₂), the oxidation state of magnesium changes. After the reaction, magnesium exists as Mg²⁺, meaning its oxidation state has risen to +2.
Understanding changes in oxidation states is crucial as it helps us identify which elements are oxidized and which are reduced in redox reactions.

Magnesium Reaction with Acids

When magnesium reacts with acids, it typically produces hydrogen gas and magnesium salts. Here's a common reaction with hydrochloric acid (HCl):
\[ \text{Mg} + 2 \text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2 \]
In this reaction, magnesium (Mg) reacts with hydrochloric acid (HCl) to produce magnesium chloride (MgCl₂) and hydrogen gas (H₂).
Before the reaction, magnesium is in its elemental form (Mg) with an oxidation state of 0. During the reaction, magnesium loses two electrons and forms Mg²⁺ with an oxidation state of +2.
At the same time, hydrogen ions (H⁺) from the acid gain electrons to form hydrogen gas (H₂). This simultaneous oxidation and reduction process defines a redox reaction.

• Magnesium is oxidized (loses electrons).
• Hydrogen ions are reduced (gain electrons).

Understanding the specific steps helps to comprehend how magnesium transforms during the reaction with acids.

Electron Transfer

Electron transfer is fundamental to redox reactions. An atom's loss of electrons is called oxidation, while the gain of electrons is called reduction. These two processes occur together in a redox reaction.
In our magnesium reaction example, magnesium atoms lose electrons (are oxidized) when they react with hydrochloric acid, forming Mg²⁺ ions. These lost electrons are gained by hydrogen ions (H⁺) from the acid, converting them into hydrogen gas (H₂).
The steps of electron transfer are:

• Magnesium atoms (Mg) lose two electrons, forming Mg²⁺ ions.
• These electrons are gained by hydrogen ions (H⁺) from the acid.
• The hydrogen ions (H⁺) are reduced to form hydrogen gas (H₂).

Understanding electron transfer helps explain the changes in oxidation states and provides a clearer picture of the redox process in a chemical reaction.
Redox reactions, including electron transfers, are crucial in many chemical processes, from biological systems to industrial applications. Recognizing how electrons move in reactions helps students grasp the fundamental nature of chemical changes.