Problem 104 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following gas mixtures is used by divers inside the sea? (a) \(\mathrm{O}_{2}+\mathrm{Ar}\) (b) \(\mathrm{O}_{2}+\mathrm{He}\) (c) \(\mathrm{O}_{2}+\mathrm{Xe}\) (d) \(\mathrm{O}_{2}+\mathrm{N}_{2}\)

Step-by-Step Solution

Answer

Divers use a mixture of \(\mathrm{O}_{2}+\mathrm{He}\) (Option b).

Step 1: Understanding the Requirement for Diving

Divers require a breathing gas mixture that is safe and minimizes the risks at high pressure underwater. Nitrogen, the main component of air, can become narcotic at deep water pressure, causing nitrogen narcosis. Helium is often used to replace nitrogen because it is less soluble and less narcotic.

Step 2: Evaluating the Options

Review the given gas mixtures: (a) \(\mathrm{O}_{2}+\mathrm{Ar}\): Argon is not used because it is more narcotic than nitrogen.(b) \(\mathrm{O}_{2}+\mathrm{He}\): Helium is non-narcotic and widely used in deep-sea diving.(c) \(\mathrm{O}_{2}+\mathrm{Xe}\): Xenon is rare and highly soluble, not used in diving.(d) \(\mathrm{O}_{2}+\mathrm{N}_{2}\): Normal air, used for shallow dives, but not recommended for deep dives.

Step 3: Conclusion

Given the analysis above, \(\mathrm{O}_{2}+\mathrm{He}\) is the best choice as it minimizes risks such as nitrogen narcosis and is common in deep-sea diving applications. Helium's properties make it favorable in mixed-gas diving.

Key Concepts

Nitrogen Narcosis

Nitrogen narcosis is a fascinating phenomenon that many divers must keep an eye on, especially during deep-diving activities. This condition is caused when nitrogen from the air mixes with other gases in a diver's blood under great pressure.
As you dive deeper, the increased water pressure enhances the solubility of nitrogen. This can lead to a narcotic effect on the diver, similar to consuming alcohol.

• It often results in impaired judgment, slower reaction time, and a false sense of security.
• Symptoms can start as shallow as 30 meters (100 feet), intensifying with depth.

To mitigate nitrogen narcosis, divers often use specialized gas mixtures to lower nitrogen levels in their breathing gas, such as helium, which helps to maintain clarity and safety underwater.

Helium Properties

Helium is not just a party balloon gas—it plays a crucial role in diving. Due to its properties, helium is the preferred component in breathing gas mixtures for deep dives. One of the fantastic features of helium is that it is less soluble in blood than nitrogen.

• This reduces the potential for narcosis, making dives safer and clearer-minded.
• Additionally, helium is lightweight, contributing to easier breathing compared to denser gases like nitrogen.

This aspect becomes pivotal in preventing breathing difficulties under the immense pressure of deep-sea diving conditions. However, helium can cause increased heat loss due to its high thermal conductivity, so divers must be cautious of becoming too cold during extended dives.

Deep-Sea Diving Techniques

Diving deep requires not only courage but also rigorous techniques to ensure safety and effectiveness. Deep-sea diving techniques have evolved, thanks to our understanding of gas mixtures and pressure impacts on the human body.
One such technique is the use of trimix, a breathing gas mixture of oxygen, helium, and nitrogen. This blend is used:

• To reduce oxygen toxicity and manage nitrogen narcosis risks.
• To optimize the dive duration and safety.

Furthermore, divers practice staged decompression, where they ascend slowly and make stops. This allows their bodies to safely expel dissolved gases and avoid decompression sickness. Advanced equipment and technology, such as dive computers, are also vital for monitoring dive depths, durations, and gas mixtures, ensuring a smoother and safer diving experience.