Molar enthelpy of a gas at various temperatures

[pearapple]

Homework Statement

I'm given the molar enthalpy of a gas at various temperatures.

For each temperature, the enthalpy at 1 bar and 100 bars of pressure is listed.

The question: The gas moves through a tube. The pressure in the tube is 100 bar. When the gas exits the tube, the pressure is 1 bar. (Hint: the enthalpy is conserved).

What is the lowest temperature at which some liquefaction takes place?

Homework Equations

The Attempt at a Solution

The chart says that at 1 bar and 77 K (liquid), the gas' enthalpy is -3407 J.

At 1 bar and 77 K (gas), the gas' enthalpy is 2161 J.

I think I'm supposed to find the temperature in the 100 bar part at which some liquifaction takes place. I am just not sure whether to use the liquid enthalpy or the gas enthalpy. Once I know the enthalpy, I can get the temperature.

 

[mark726]

your first step would be to carefully analyze the given information and understand the question at hand. Based on the given information, it seems that the gas is undergoing a change in pressure and temperature as it moves through the tube. The enthalpy of the gas is conserved, meaning it remains constant throughout this process.

To answer the given question, you will need to use the given enthalpy values at different temperatures and pressures to determine the lowest temperature at which some liquefaction takes place. This can be done by using the formula for enthalpy change (ΔH = H2 - H1), where H2 is the enthalpy at the exit pressure (1 bar) and H1 is the enthalpy at the entry pressure (100 bar).

Since the gas is undergoing a change from high pressure to low pressure, it is likely that it will experience a decrease in temperature. This decrease in temperature will eventually reach a point where the gas will start to liquefy. Therefore, you will need to use the enthalpy values for the gas at different temperatures to determine the lowest temperature at which liquefaction occurs.

In summary, to solve this problem, you will need to use the formula for enthalpy change and the given enthalpy values at different temperatures to determine the lowest temperature at which some liquefaction takes place. It is important to carefully analyze the given information and use your understanding of thermodynamics to arrive at the correct answer.