Given below are the critical temperatures of some of the gases :
Gas Critical temperature (K) He 5.2 CH4 190.0 CO2 304.2 NH3 405.5
The gas showing least adsorption on a definite amount of charcoal is
Given below are the critical temperatures of some of the gases :
| Gas | Critical temperature (K) |
|---|---|
| He | 5.2 |
| CH4 | 190.0 |
| CO2 | 304.2 |
| NH3 | 405.5 |
The gas showing least adsorption on a definite amount of charcoal is
- He
- CH4
- CO2
- NH3
The Correct Option is A
Approach Solution - 1
The adsorption of gases on a solid surface depends on several factors, one of which is the critical temperature of the gas. Critical temperature is the temperature above which a gas cannot be liquefied, regardless of pressure. Generally, gases with higher critical temperatures are more easily adsorbed because they are more easily liquefied or condensed and have stronger interaction with the surface.
Let's examine the critical temperatures of the gases given:
| Gas | Critical Temperature (K) |
|---|---|
| He | 5.2 |
| CH4 | 190.0 |
| CO2 | 304.2 |
| NH3 | 405.5 |
From the table, we see the critical temperatures are as follows:
- Helium (He): 5.2 K
- Methane (CH4): 190.0 K
- Carbon dioxide (CO2): 304.2 K
- Ammonia (NH3): 405.5 K
Among these gases, helium (He) has the lowest critical temperature at 5.2 K. This means helium is the least easily condensed and thus has the weakest interactions with the surface of the charcoal. Therefore, helium will exhibit the least adsorption on a definite amount of charcoal compared to the other gases.
Conclusion: The gas showing the least adsorption on charcoal is Helium (He).
Approach Solution -2
Extent of adsorption ∝ TC (critical temperature)
∵ Lower the TC, Lower will be the adsorption
Hence, Helium shows least adsorption on a definite amount of charcoal.
So, the correct option is (A): He.
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Concepts Used:
Temperature Dependence of Resistance
The temperature dependence of resistance is a fundamental property of all materials that conduct electricity. Generally, the resistance of a conductor increases with an increase in temperature. This phenomenon is known as a positive temperature coefficient of resistance.
The reason for this temperature dependence of resistance is related to the interaction of electrons with the crystal lattice of the material. At lower temperatures, the lattice vibrations are minimal, and the electrons are free to move through the material with minimal scattering. This results in a low resistance to the flow of current. However, as the temperature increases, the lattice vibrations increase, causing the electrons to scatter more frequently, which increases resistance.
This phenomenon is governed by the relationship between resistance and temperature known as the temperature coefficient of resistance. The temperature coefficient of resistance is defined as the rate at which resistance changes with respect to temperature. The temperature coefficient of resistance is positive for most metals and semiconductors, meaning that resistance increases with increasing temperature.
However, there are a few materials, such as carbon and certain semiconductors, which exhibit a negative temperature coefficient of resistance. In these materials, the resistance decreases as the temperature increases.
The temperature dependence of resistance has important practical implications in the design and operation of electrical circuits and devices. For example, it is essential to consider the effect of temperature on the resistance of electronic components to ensure reliable and efficient operation of devices over a range of temperatures.