Problem 37 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Arrange the following in : \(\mathrm{CO}_{2}, \mathrm{~N}_{2} \mathrm{O}_{5}, \mathrm{SiO}_{2}, \mathrm{SO}_{3}\) in the order of increasing acidic character. [1988-1 Mark]

Step-by-Step Solution

Answer

Increasing acidic order: SiO2, CO2, N2O5, SO3.

Step 1 - Understanding Acidic Character

Acidic character in oxides often depends on the metallic vs. non-metallic nature of the central atom. Non-metallic oxides tend to be more acidic.

Step 2 - Identify the Nature of the Central Atom

Identify whether the central atom is a metal or non-metal: CO2 and N2O5 have non-metallic central atoms (Carbon and Nitrogen), while SiO2 and SO3 have non-metallic central atoms (Silicon and Sulfur).

Step 3 - Determine Oxides' Acidic Character

Silicon dioxide (SiO2) is weakly acidic and can also act as an amphoteric oxide. CO2 is more acidic, forming carbonic acid in water. N2O5 is strongly acidic, forming nitric acid in water. SO3 is the most acidic, forming sulfuric acid in water.

Step 4 - Arrange in Increasing Acidic Order

Based on the acidic character: SiO2 (weakly acidic) < CO2 < N2O5 < SO3 (most acidic).

Key Concepts

Non-metallic oxides

Non-metallic oxides are compounds composed of oxygen and a non-metal. These oxides usually exhibit acidic properties when they react with water.
For instance, carbon dioxide (CO₂) interacts with water to create carbonic acid, whereas sulfur trioxide (SO₃), when dissolved in water, forms sulfuric acid. Both are typical reactions demonstrating that non-metallic oxides can contribute to acidic environments.
Non-metallic oxides can generally be found among non-metal elements such as nitrogen, carbon, sulfur, and silicon. They're interesting as they offer insight into how elements react when combined with oxygen. By understanding these reactions, we can better grasp why some non-metallic oxides are more acidic than others, helping to predict their behavior in various chemical environments.

Oxides acidity comparison

When comparing the acidity of oxides, examining their behavior in water provides much insight.
The more vigorously an oxide reacts with water to form an acid, the stronger its acidic character. Here are some points to consider:

• Sulfur trioxide (SO₃): When dissolved, it forms sulfuric acid, demonstrating a very strong acidic nature.
• Nitrogen pentoxide (N₂O₅): Forms nitric acid in water, indicating strong acidity.
• Carbon dioxide (CO₂): Reacts with water to create carbonic acid, having moderate acidic behavior.
• Silicon dioxide (SiO₂): It's barely reactive with water and thus shows weak acidic (and amphoteric) properties.

These reactions help in recognizing the increasing order of acidic character. This comparison is useful not just for academic purposes but also for practical applications like predicting how these substances might interact in different settings.

Metallic vs. Non-metallic properties

Understanding the difference between metallic and non-metallic properties is crucial in chemistry because it aids in predicting the nature of oxides. Metallic elements, like sodium or magnesium, form basic oxides that often dissolve in water to produce alkaline solutions. In contrast, non-metallic elements typically form acidic oxides.
For instance, sodium oxide (Na₂O) will dissolve in water and increase the pH, giving a basic solution due to the formation of hydroxide ions. On the other hand, carbon dioxide, as a non-metallic oxide, will lower the pH by forming an acidic solution.
Thus, recognizing the property differences between metallic and non-metallic elements can help in understanding how elements interact with oxygen to form either acidic or basic oxides. Knowing these interactions is vital in chemistry, impacting fields ranging from environmental science to industry, wherever these substances are utilized.