2.00 mole of an ideal, monatomic gas

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In summary, the conversation discusses the problem of calculating delta S for a system that undergoes an irreversible expansion against a constant external pressure. The hint suggests breaking up the expansion into two reversible steps to make use of the standard thermo equations. The conversation also mentions the use of the ideal gas law and delta H for reversible processes.
  • #1
nkk2008
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Ok, so here is my problem:

Suppose 2.00 mole of an ideal, monatomic gas is initially at a pressure of 3.00 atm and a temperature of 350K. It is expanded irreversibly and adiabatically against a constant external pressure of 1.00 atm until the volume has doubled.

A) Calculate delta S for the system, the surroundings, and the universe (i.e. total).
Hint: To find delta S of system, consider breaking up the expansion into two steps. Based on the properties of and relationships for delta S, think of why you can and must do this.

B)If the absolute entropy per mole of the gas before the expansion is 158.2 J/K mol, calculate delta Gibbs free energy for the process.
Hint: You must use the generally defined relationship for delta G.

We do not want the answers, but my friend and I have no idea where to start. IF you could at least tell us what the hint in part A means we could go from there.

Thank you.
 
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  • #2


The standard thermo equations apply only to systems in equilibrium, so they're of little use against irreversible processes. A neat trick is to split an irreversible process into multiple reversible parts. (For example, we might extract work via a piston, but then dump that energy right back in as heat.) The starting and ending states are the same, but the requirement of reversibility is now fulfilled and the equations are now tractable. Is this enough to get you started?
 
  • #3


But how do I deal with any changes in temperature? Are there any? In class we learned that delta s equaled q/t, where q was equal to delta h for reversible processes
 
  • #4


Remember that it's an ideal gas, and apply the ideal gas law if it simplifies things.
 

Related to 2.00 mole of an ideal, monatomic gas

1. What does it mean to have "2.00 mole" of a gas?

Having 2.00 moles of a gas means that there are 2.00 times Avogadro's number (6.022 x 10^23) of gas particles present in the sample. This is a unit of measurement used in chemistry to indicate the amount of a substance.

2. What is an ideal gas?

An ideal gas is a hypothetical gas that follows the ideal gas law, which describes the relationship between pressure, volume, temperature, and the number of moles of a gas. An ideal gas does not exist in reality, but it serves as a useful model for understanding the behavior of real gases.

3. Why is the gas assumed to be monatomic?

A monatomic gas is one that consists of single atoms and does not form molecules. In this context, it is assumed that the gas is monatomic because it simplifies the calculations and makes it easier to apply the ideal gas law.

4. How does the number of moles affect the behavior of the gas?

The number of moles of a gas affects its behavior by determining the amount of gas particles present in the sample. This, in turn, affects the pressure, volume, and temperature of the gas according to the ideal gas law.

5. What are some examples of monatomic gases?

Some common examples of monatomic gases include helium, neon, argon, krypton, and xenon. These gases are all found in the noble gas family on the periodic table and exist as single atoms in their gaseous state.

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