When can you assume something is an ideal gas?

For a gas to be “ideal” there are four governing assumptions: The gas particles have negligible volume. The gas particles are equally sized and do not have intermolecular forces (attraction or repulsion) with other gas particles. The gas particles move randomly in agreement with Newton’s Laws of Motion.

When can you not assume ideal gas?

The ideal gas law fails at low temperature and high-pressure because the volume occupied by the gas is quite small, so the inter-molecular distance between the molecules decreases. And hence, an attractive force can be observed between them.

Can the entropy of an ideal gas change during an isothermal process?

Yes, ΔS is not a function of only temperature, so it is not zero. So if the gas expands in the isothermal process, then yes, it will have increased entropy.

Why does the ideal gas law work?

Please notice that “Ideal Gas Law” is “ideal” because it only works when you assume the conditions are “ideal”. And well, all gases behave ideally under conditions of high temperature and low pressure. At low temperature, there are less gas molecules in a certian volume.

What are the limits of the Ideal Gas Law?

Since the particles of an ideal gas have no volume, a gas should be able to be condensed to a volume of zero. Reality check: Real gas particles occupy space. A gas will be condensed to form a liquid which has volume. The gas law no longer applies because the substance is no longer a gas!

How does the Ideal Gas Law work?

The ideal gas law has the form: PV=nRT , where R is the universal gas constant, and with it we can find values of the pressure P, volume V, temperature T, or number of moles n under a certain ideal thermodynamic condition. Typically, you are given enough parameters to calculate the unknown.

What is the work done in an isothermal free expansion of an ideal gas?

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In other words, in isothermal process ∆T = 0. Free expansion of a gas occurs when it is subjected to expansion in a vacuum (pex=0). During free expansion of an ideal gas, the work done is 0 be it a reversible or irreversible process.

What is the change in entropy of the surroundings when ideal gas expands?

In the reversible case, the change in entropy of the surroundings is equal and opposite to the change in the system, so the change in entropy of the universe is zero. In the free expansion, Q = 0, so the entropy of the surroundings does not change and the change in entropy of the universe is equal to ΔS for the system.

What is isothermal expansion in a gas?

Isothermal means the temperature does not change. Expansion means the volume has increased. Therefore, isothermal expansion is the increase in volume under constant-temperature conditions. In this situation, the gas does work, so the work is negatively-signed because the gas exerts energy to increase in volume.

What happens to the temperature of an ideal gas during expansion?

If the pressure of an ideal gas is kept constant, then the temperature must increase as the gas expands. (PV/T = constant.) Heat must be added during the expansion process.

What is the work done by an ideal gas under isothermal conditions?

During isothermal conditions, the change in internal energy ΔU is 0 for only an ideal gas, so efficient work done is entirely transformed into efficient heat flow. wrev is the most efficient work possible (reversible work) in J.

What are the properties of ideal gases?

An ideal gas possesses atoms and molecules that are highly elastic. Since the molecules of an ideal gas move faster than any other source, there is an absence of any intermolecular force of attraction between the elements.