Problem 198 - A Complete Resource Book in Chemistry for JEE Main

Question

Which one of the following statements regarding helium is correct? (a) it is used in gas-cooled nuclear reactors (b) it is used to produce and sustain powerful super conducting magnets (c) it is used as a cryogenic agent for carrying out experiments at low temperatures (d) all are correct

Step-by-Step Solution

Answer

Option (d) is correct; all statements are true.

Step 1: Analyze Statement (a)

Helium is indeed used in gas-cooled nuclear reactors. It is an inert gas that helps in cooling due to its high heat capacity and the fact that it doesn't become radioactive easily. Therefore, statement (a) is correct.

Step 2: Analyze Statement (b)

Helium is used in producing and maintaining superconducting magnets. Superconducting magnets require very low temperatures to function efficiently, and liquid helium, being capable of reaching such temperatures, is often used. Thus, statement (b) is correct.

Step 3: Analyze Statement (c)

Helium is commonly used as a cryogenic agent because of its ability to remain in a liquid state at extremely low temperatures. This makes it suitable for low-temperature experiments. Hence, statement (c) is correct.

Step 4: Evaluate Statement (d)

Each of the statements (a), (b), and (c) was found to be correct in the previous steps. Therefore, statement (d), which asserts that all are correct, is also true.

Key Concepts

Gas-cooled nuclear reactors

In gas-cooled nuclear reactors, helium plays a crucial role as a coolant. Nuclear reactors are complex systems where heat generated from nuclear fission needs to be controlled effectively. Helium, a noble gas, is chosen for this purpose due to its high heat capacity, meaning it can absorb a lot of heat without getting hot. Unlike liquid coolants, helium remains in a gaseous state and can efficiently remove heat from the reactor.
Moreover, helium does not readily become radioactive, making it a safe option for nuclear reactor cooling. Some other reasons for selecting helium include:

• It is chemically inert, so it doesn't react with reactor materials, reducing the risk of corrosion or chemical reactions.
• Helium can be circulated easily within the nuclear reactor's systems, thanks to its low density.
• It's a stable choice over a wide range of temperatures.

Gas-cooled reactors benefit from helium's characteristics, making them more efficient and safe for energy production.

Superconducting magnets

Superconducting magnets are a fascinating phenomenon in physics, crucial in several advanced technologies like MRI machines and particle accelerators. These magnets require extremely low temperatures to function, which is where helium comes into play. Helium is utilized largely in its liquid form to cool down the materials to superconductive states.
At temperatures near 4 Kelvin (-269 degrees Celsius), certain materials exhibit superconductivity, where they can conduct electricity without any resistance. Liquid helium aids in achieving these ultra-low temperatures necessary for:

• Maintaining a stable superconducting state.
• Reducing energy losses during magnetic field generation.
• Ensuring the longevity of the superconductive magnets.

Without liquid helium, the practicality of superconducting magnets would be severely limited, as it helps maintain their efficiency and functionality.

Cryogenic agent

Helium is an excellent cryogenic agent due to its ability to exist as a liquid at extremely low temperatures. In scientific experiments and industrial processes requiring ultra-low temperatures, helium is used to create and manage these conditions.
Cryogenics deals with the behavior of materials at temperatures below -150 degrees Celsius. As a cryogenic agent, helium allows researchers and engineers to study physical phenomena that only occur at these low temperatures. Some notable uses include:

• Testing the properties of materials and components used in space exploration.
• Cryopreservation, aiding in the storage and preservation of biological samples.
• Creating environments for highly sensitive low-temperature physics experiments.

Thanks to helium's unique properties including remaining a liquid at temperatures close to absolute zero, it is an indispensable tool in the field of cryogenics.