Question

In: Physics

drive the change in entropy for an ideal gas

drive the change in entropy for an ideal gas

Solutions

Expert Solution

For an ideal gas, . Thus

Using the equation of state for an ideal gas ( ), we can write the entropy change as an expression with only exact differentials:

(5..2)

We can think of Equation (5.2) as relating the fractional change in temperature to the fractional change of volume, with scale factors and ; if the volume increases without a proportionate decrease in temperature (as in the case of an adiabatic free expansion), then increases. Integrating Equation (5.2) between two states ``1'' and ``2'':

For a perfect gas with constant specific heats

In non-dimensional form (using )

(5..3)

Equation 5.3 is in terms of specific quantities. For moles of gas,

This expression gives entropy change in terms of temperature and volume. We can develop an alternative form in terms of pressure and volume, which allows us to examine an assumption we have used. The ideal gas equation of state can be written as

Taking differentials of both sides yields

Using the above equation in Eq. (5.2), and making use of the relations ; , we find

or

Integrating between two states 1 and 2

(5..4)

Using both sides of (5.4) as exponents we obtain

(5..5)

Equation (5.5) describes a general process. For the specific situation in which , i.e., the entropy is constant, we recover the expression . It was stated that this expression applied to a reversible, adiabatic process. We now see, through use of the second law, a deeper meaning to the expression, and to the concept of a reversible adiabatic process, in that both are characteristics of a constant entropy, or isentropic, process.


Related Solutions

a) Calculate the change in entropy on heating an ideal gas from 300K to 500K at...
a) Calculate the change in entropy on heating an ideal gas from 300K to 500K at constant pressure. b) Calculate the change in entropy on heating an ideal gas from 300K to 500K at constant volume. c) why these answers are different. Please explain each steps.
a). In the ideal gas mixture, is there any way the process entropy change equals zero?...
a). In the ideal gas mixture, is there any way the process entropy change equals zero? b) Calculate μ, the Joule-Kelvin coefficient for a Van der Waals gas.
According to the Sackur–Tetrode formula, the entropy of an ideal monatomic gas grows with
According to the Sackur–Tetrode formula, the entropy of an ideal monatomic gas grows with the mass of the atoms. Thus the entropy of a volume of argon is much greater than the same volume of helium (at the same T and p). Can you explain this in terms of information entropy?    
what is the change in entropy, enthalpy and gibbs free energy when 1 L of ideal...
what is the change in entropy, enthalpy and gibbs free energy when 1 L of ideal gas i, 3 L of ideal gas j and 4 L of ideal gas k, each at 1 atm and room temperature (298.15K) blend to form a gas mixture at the same conditions?
Calculate the change in Entropy
A 288 kg block of ice at 0∘C is placed in a large lake the temperature of the lake is just slightly higher than 0∘C and the ice melts very slowly.   i) what is the entropy change of ice  
1. For an ideal gas at a constant temperature, which variable change corresponds directly to how...
1. For an ideal gas at a constant temperature, which variable change corresponds directly to how much work can be extracted from an engine process? Explain why. 2. You learned how the Doppler effect can be used to show how sound waves will change their frequency when the source object is moving. How can this knowledge be applied toward studying how stars move? 3. A lightning rod is a pointed copper rod mounted on top of a building and welded...
1 Ideal Gas Law The ideal gas law is familiar to anyone who has taken a...
1 Ideal Gas Law The ideal gas law is familiar to anyone who has taken a college chemistry course: P V = νRT. This problem will show you why the ideal gas law has this form. We can arrive at this expression just by using classical mechanics! Consider a box of volume V containing N particles, each having mass m, that are moving horizontally with average speed v. The particles bounce back and forth between the end walls of the...
What is an ideal gas law? How did scientist arrive at the present day ideal gas...
What is an ideal gas law? How did scientist arrive at the present day ideal gas equation. (Hint: explain different gas laws and how you come to ideal gas law equation using all the laws)
For the ideal gas law to be most applicable, it is best for the gas to...
For the ideal gas law to be most applicable, it is best for the gas to exist at?
An ideal gas (which is is a hypothetical gas that conforms to the laws governing gas...
An ideal gas (which is is a hypothetical gas that conforms to the laws governing gas behavior) confined to a container with a massless piston at the top. (Figure 2)  A massless wire is attached to the piston. When an external pressure of 2.00 atm is applied to the wire, the gas compresses from 5.90 to 2.95 L . When the external pressure is increased to 2.50 atm, the gas further compresses from 2.95 to 2.36 L . In a separate...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT