Problem 41 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is produced when magnesium reacts with hot concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4} ?\) (a) \(\mathrm{H}_{2}\) (b) \(\mathrm{S}\) (c) \(\mathrm{MgO}\) (d) \(\mathrm{SO}_{2}\)

Step-by-Step Solution

Answer

(d) \(\mathrm{SO}_{2}\) is produced.

Step 1: Understanding the Reaction

When magnesium reacts with hot concentrated sulfuric acid (\(\mathrm{H}_{2} \mathrm{SO}_{4}\)), it's a redox reaction where magnesium acts as a reducing agent. This means it donates electrons, reducing another substance, and in this case, producing sulfur dioxide as one of the products.

Step 2: Write the Reaction Equation

The chemical equation for the reaction of magnesium with hot concentrated sulfuric acid is:\[\mathrm{Mg} + \mathrm{2H}_2\mathrm{SO}_4 \rightarrow \mathrm{MgSO}_4 + 2\mathrm{H}_2\mathrm{O} + \mathrm{SO}_2\]This equation shows that sulfur dioxide (\(\mathrm{SO}_2\)) is formed.

Step 3: Identifying the Product Formed

From the equation, we can see that \(\mathrm{SO}_2\) (sulfur dioxide) is one of the products formed when magnesium reacts with hot concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4}\). Other possible products like \(\mathrm{MgO}\) or \(\mathrm{H}_2\) are not formed in this reaction.

Key Concepts

Magnesium Reactions

Magnesium is a lightweight metal commonly used in various chemical reactions to study basic principles of chemistry. When magnesium takes part in reactions, it often acts as a reducing agent due to its willingness to donate electrons. This donation lowers the charge of another element or molecule, causing the reducing agent being oxidized itself.
Upon exposure to acids, magnesium reacts vigorously, generating visible signs such as bubbles or heat. In reactions involving magnesium, always ensure proper safety measures as reactions can be exothermic or explosive. Understanding how magnesium behaves in these scenarios is essential, especially when handling concentrated acids.

Sulfuric Acid Chemistry

Sulfuric acid (\(\mathrm{H}_{2} \mathrm{SO}_{4}\)) is a strong acid widely used in industrial processes, making it a staple chemical in chemistry labs. It has a dehydrating property and is a powerful oxidizing agent when concentrated and heated, introducing unique characteristics to its reactions.
When concentrated sulfuric acid is heated, it aggressively interacts with metals like magnesium, transforming into sulfur dioxide (\(\mathrm{SO}_2\)), water, and other compounds. In this reaction, sulfuric acid experiences a change in oxidation state of its sulfur component, typically contributing to gas evolution such as sulfur dioxide. Such reactions emphasize the importance of understanding acid strengths and their reactivity for practical applications.

Chemical Equations

Chemical equations are symbolic representations to understand chemical reactions better. They show the substances involved, commonly known as reactants and products, and the quantities of molecules or atoms involved.
In the reaction between magnesium and hot concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4}\), the equation\[\mathrm{Mg} + \mathrm{2H}_2\mathrm{SO}_4 \rightarrow \mathrm{MgSO}_4 + 2\mathrm{H}_2\mathrm{O} + \mathrm{SO}_2\]helps us visualize how matter transforms.

• Magnesium reacts to form magnesium sulfate (\(\mathrm{MgSO}_4\)).
• Water (\(\mathrm{H}_2\mathrm{O}\)) is produced, indicating the release of hydrogen atoms.
• Sulfur dioxide (\(\mathrm{SO}_2\)) forms as a result of sulfuric acid's decomposition.

Balancing chemical equations like this ensures mass conservation, reflecting that matter is neither created nor destroyed in reactions.