Problem 18 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Which of the following is coloured (a) NO (b) \(\mathrm{N}_{2} \mathrm{O}\) (c) \(\mathrm{SO}_{3}\) (d) None

Step-by-Step Solution

Answer

The correct option is (d) None, as all the given gases are usually colorless.

Step 1: Analyze Color of Gases

To determine which of the given gases is colored, let's review the properties of the molecules. Most gases like NO, N2O, and SO3 are colorless. However, some gases are known to be colored due to the presence of unpaired electrons or specific bonding.

Step 2: Review of NO

Nitric oxide (NO) is a diatomic molecule with a free radical electron, which can give rise to color under certain conditions. However, NO is generally considered to be colorless when it is not reacting or oxidizing.

Step 3: Review of N2O

Nitrous oxide (N2O), commonly known as 'laughing gas,' is colorless. It is primarily used as an anesthetic in medicine and is not noticeable by color.

Step 4: Review of SO3

Sulfur trioxide (SO3) is also a colorless gas under normal conditions. It reacts with water to form sulfuric acid but does not have a visible color itself.

Step 5: Conclusion

Since NO, N2O, and SO3 are determined to be colorless based on their chemical properties and typical conditions, the short answer would be that none of the provided options are colored gases.

Key Concepts

Nitric oxide (NO) properties

Nitric oxide (NO) is a simple diatomic molecule comprised of one nitrogen atom and one oxygen atom. It is well-known for its role as a signaling molecule in mammals, playing key roles in various physiological and pathological processes. One unique attribute of NO is its free radical form. This means it contains an unpaired electron, which can sometimes influence its properties.
In terms of appearance, nitric oxide is generally considered colorless under normal conditions. However, NO can exhibit color in gaseous states when it starts to react, especially when it forms nitrogen dioxide (NO extsubscript{2}), a brown gas. This transformation typically occurs when NO is exposed to oxygen, and the resulting mixture can appear reddish-brown.

• Colorless when unreacted
• Can form colored reactions upon oxidation
• Reactive due to unpaired electron leading to other chemical transformations

As a reactive species, NO is important in environmental chemistry, where it contributes to phenomena such as air pollution.

Nitrous oxide (N2O) characteristics

Nitrous oxide, often referred to as 'laughing gas', is a well-known compound due to its uses in the medical and industrial fields. This compound is composed of two nitrogen atoms bonded to one oxygen atom. Its most common application is as an anesthetic, providing pain relief and sedation.
Physically, nitrous oxide is known to be colorless, odorless, and non-flammable under normal conditions. These characteristics make it suitable for use in dentistry and surgeries. Unlike nitric oxide, nitrous oxide does not undergo reactions that lead to any visible color changes with typical environmental exposure.

• Colorless gas
• Widely used as an anesthetic
• Stable and non-reactive under most conditions

It's important to handle with care as it can contribute to greenhouse gas emissions contributing to environmental concerns.

Sulfur trioxide (SO3) properties

Sulfur trioxide (SO extsubscript{3}) is a chemical compound that forms part of the sulfur oxide group known for its significance in industrial chemistry, mainly in the production of sulfuric acid. It is made up of one sulfur atom and three oxygen atoms, presenting a trigonal planar geometry.
In its gaseous state, SO extsubscript{3} remains colorless. However, it is highly reactive, particularly with water, where it forms sulfuric acid, a dense, heavy liquid that is colorless and highly corrosive. This reaction explains its significance in acid rain formation, which is an environmental concern.

• Colorless gas
• Highly reactive with water
• Key precursor for sulfuric acid

Despite its lack of color, SO extsubscript{3} should be handled with caution due to its reactivity and importance in atmospheric chemistry.