Question

The gas that is heated up during Joule-Thomson effect at ordinary temperature is: (a) \(\mathrm{O}_{2}\) (b) \(\mathrm{CO}_{2}\) (c) \(\mathrm{H}_{2}\) (d) \(\mathrm{SO}_{2}\)

Short answer

The gas that heats up during the Joule-Thomson effect at normal temperature is Hydrogen (\(\mathrm{H}_{2}\)).

Step-by-step solution

Understanding the Joule-Thomson effect

Recognize that the Joule-Thomson effect states that gases cool upon expansion, but Hydrogen and Helium heat up under normal conditions. This means that for the mentioned gases, when they expand, their temperature will increase.

Identifying the correct gas

Look at the given options. The gases given are Oxygen (\(\mathrm{O}_{2}\)), Carbon Dioxide (\(\mathrm{CO}_{2}\)), Hydrogen (\(\mathrm{H}_{2}\)), and Sulfur Dioxide (\(\mathrm{SO}_{2}\)). Among these, Hydrogen (\(\mathrm{H}_{2}\)) is the gas that would heat up when expanded under normal conditions according to the Joule-Thomson effect.

Key concepts

Gas Expansion

Gas expansion is a crucial concept when studying gas behavior under different conditions. When a gas expands, it moves from a region of higher pressure to lower pressure. This process can affect the temperature and internal energy of the gas.
The Joule-Thomson effect specifically looks at what happens to the temperature of gases when they expand without exchanging heat with the environment (an adiabatic process). In most cases, gases cool down when they expand because their internal energy is spread over a larger volume.
Understanding gas expansion helps in applications like refrigeration and air conditioning, where it's important to manipulate temperature changes without external heat exchange.

Temperature Change in Gases

Gases can experience a temperature change during expansion due to the Joule-Thomson effect. This effect describes how a gas's temperature responds when it expands and does no work or exchanges heat with its surroundings.
For most gases, expansion results in cooling. However, some gases, like hydrogen and helium, behave differently under certain conditions, warming up instead.
This temperature change depends on several factors, including the type of gas and the specific conditions of the expansion, such as pressure and temperature.

• For many gases: Expansion → Cooling
• For hydrogen and helium: Expansion → Warming (under normal conditions)

Hydrogen Gas Behavior

Hydrogen gas exhibits unique behavior during expansion, especially highlighted by the Joule-Thomson effect. Unlike most gases, hydrogen heats up when it expands under typical atmospheric conditions. This is due to its very low inversion temperature.
The inversion temperature is the point at which the cooling effect switches to a heating effect for a gas. Since hydrogen’s inversion temperature is below room temperature, it behaves unusually, heating upon expansion. This characteristic sets hydrogen apart from gases like oxygen and carbon dioxide.
Such behavior is critical when designing systems that use hydrogen, ensuring safety and efficiency in processes like fuel storage, gas pipelines, and energy production.

Joule-Thomson Coefficient

The Joule-Thomson coefficient is a crucial value in understanding how a gas will behave when it expands. It determines whether a gas will cool or heat under adiabatic expansion.
This coefficient is calculated based on the specific properties of the gas, such as its specific heat and pressure. It indicates the rate of temperature change per unit pressure drop.

• Positive coefficient: Gas cools on expansion.
• Negative coefficient: Gas heats on expansion.

For hydrogen, the Joule-Thomson coefficient is negative under normal conditions, meaning it heats up upon expansion, unlike many other gases with a positive coefficient.
Understanding this coefficient helps in designing processes that involve gas expansion, such as in refrigeration systems and gas liquefaction.