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Expand \(1.00\) mol of an monatomic gas initially at \(5.00 \mathrm{kPa}\) and \(600 \mathrm{~K}\) from initial volume \(V_{i}=1.00 \mathrm{~m}^{3}\) to final volume \(V_{f}=\) \(2.00 \mathrm{~m}^{3}\). At any instant during the expansion, the pressure \(p\) and volume \(V\) of the gas are related by \(p=5.00 \exp \left[\left(V_{i}-V\right) / a\right]\), with \(p\) in kilopascals, \(V_{i}\) and \(V\) in cubic meters, and \(a=1.00 \mathrm{~m}^{3}\). What are the final (a) pressure and (b) temperature of the gas? (c) How much work is done by the gas during the expansion? (d) What is \(\Delta S\) for the expansion? (Hint: Use two simple reversible processes to find \(\Delta S .\) )

Short Answer

Expert verified
(a) Final pressure is 1.8395 kPa; (b) Final temperature is 442.49 K; (c) Work done is 3.1605 kJ; (d) ΔS is approximately 5.76 J/K.

Step by step solution

01

Determine Final Pressure

The pressure-volume relationship is given by \( p = 5.00 \exp\left[\frac{V_i - V}{a}\right] \). Substitute \( V_f = 2.00 \mathrm{~m}^3 \), \( V_i = 1.00 \mathrm{~m}^3 \), and \( a = 1.00 \mathrm{~m}^3 \) into the equation:\[ p_f = 5.00 \exp\left[\frac{1.00 - 2.00}{1.00}\right] = 5.00 \exp(-1) \approx 5.00 \times 0.3679 \approx 1.8395 \mathrm{~kPa} \]
02

Determine Final Temperature

For a monatomic ideal gas, we can use the ideal gas law \( PV = nRT \). With the final conditions \( p_f = 1.8395 \mathrm{~kPa} \), \( V_f = 2.00 \mathrm{~m}^3 \), and \( n = 1.00 \mathrm{~mol} \), we calculate \( T_f \). First, convert \( p_f \) to \( \mathrm{Pa} \) by multiplying by 1000:\[ p_f = 1.8395 \times 1000 = 1839.5 \mathrm{~Pa} \]Then use the ideal gas law:\[ 1839.5 \times 2.00 = 1.00 \times 8.314 \times T_f \]Solving for \( T_f \):\[ 3679 = 8.314 T_f \rightarrow T_f = \frac{3679}{8.314} \approx 442.49 \mathrm{~K} \]
03

Calculate Work Done by the Gas

The work done \( W \) is given by the integral \( W = \int_{V_i}^{V_f} p \,dV \). Substituting the expression for \( p \):\[ W = \int_{1.00}^{2.00} 5.00 \exp\left[\frac{1-V}{1}\right] dV = 5.00 \int_{1.00}^{2.00} \exp(1-V) dV \]The integral becomes:\[ W = 5.00 \left[-\exp(1-V) \right]_{1}^{2} = 5.00 \left[-\exp(-1) + \exp(0) \right] \approx 5.00 \left[-0.3679 + 1 \right] = 5.00 \times 0.6321 = 3.1605 \mathrm{~kJ} \]
04

Calculate Change in Entropy

For part \((d)\), use the hint of reversible processes to simplify entropy calculation. Consider two processes: isothermal expansion to \( V_f \) and isochoric cooling back to \( T_f \).First calculate entropy change for the isothermal process:\[ \Delta S_T = nR \ln\left(\frac{V_f}{V_i}\right) = 1.00 \times 8.314 \ln\left(\frac{2.00}{1.00}\right) \approx 5.76 \mathrm{~J/K} \]Then consider the isochoric process with no volume change, only temperature:\[ \Delta S_V = n \int \frac{C_v}{T} dT = 0 \] since \( T_i = 600 \mathrm{~K} \) and \( V_i = V_f \)Summing gives total entropy change:\[ \Delta S = \Delta S_T + \Delta S_V \approx 5.76 \mathrm{~J/K} \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Pressure-Volume Relationship
The pressure-volume relationship is an important concept in thermodynamics, especially for understanding the behavior of gases during expansion or compression. In this context, the relationship is described by the equation:\[ p = 5.00 \exp\left[\frac{V_i - V}{a}\right] \]where:- \(p\) is the pressure of the gas,- \(V\) is the volume,- \(V_i\) is the initial volume,- \(a = 1.00\, \mathrm{m}^3\) is a constant.This equation highlights how the pressure decreases exponentially as the volume increases. When the gas expands from the initial volume to the final volume, the pressure changes accordingly. This relationship informs us that as the gas expands, its particles occupy more space, leading to a reduction in pressure. This exponential relationship allows us to calculate the final pressure of the gas after expansion, revealing that it is approximately 1.8395 kPa when the gas has expanded to a volume of 2.00 m³.
Ideal Gas Law
The ideal gas law is a fundamental principle in thermodynamics that describes the relationship between pressure, volume, and temperature of a given amount of gas. It is given by the formula:\[ PV = nRT \]where:- \(P\) is the pressure,- \(V\) is the volume,- \(n\) is the number of moles of the gas,- \(R\) is the ideal gas constant (8.314 J/mol·K),- \(T\) is the temperature in Kelvin.Using this law, you can find unknown variables if other variables are known. For this exercise, knowing the final pressure, volume, and number of moles allows us to solve for the final temperature. The conversion from kPa to Pa (since 1 kPa = 1000 Pa) is crucial before applying the ideal gas law. After applying the values, the temperature of the gas is calculated to be approximately 442.49 K.
Work Done by Gas
Work done by a gas during expansion or compression is calculated using the integral of pressure with respect to volume:\[ W = \int_{V_i}^{V_f} p \, dV \]In this specific problem, the expression for pressure as a function of volume is given by:\[ p = 5.00 \exp\left[\frac{V_i - V}{a}\right] \]To find the work done during expansion, you substitute this expression into the equation for work and integrate from the initial to the final volume. This yields:\[ W = 5.00 \left[-\exp(1-V) \right]_{1}^{2} \]Solving this integral gives the work done as approximately 3.1605 kJ. This means energy is transferred by the gas as it expands, moving the particles and exerting a force over the change in volume.
Change in Entropy
Entropy is a measure of disorder or randomness in a system, and the change in entropy reflects how the distribution of energy in the system has evolved. In this context, the change in entropy \( \Delta S \) can be calculated by considering reversible processes.For an isothermal process where the temperature remains constant while the volume changes, the change in entropy \( \Delta S_T \) is given by:\[ \Delta S_T = nR \ln\left(\frac{V_f}{V_i}\right) \]In this case, using one mole of gas and the R constant, we find the isothermal entropy change is approximately 5.76 J/K.In an isochoric process (constant volume), only the temperature changes, and since this doesn't apply to our final condition (as the volume changes), the entropy change for this segment is effectively zero. Therefore, the total entropy change is mainly from the isothermal expansion
and amounts to around 5.76 J/K.

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Most popular questions from this chapter

A box contains \(N\) identical gas molecules equally divided between its two halves. For \(N=50\), what are (a) the multiplicity \(W\) of the central configuration, (b) the total number of microstates, and (c) the percentage of the time the system spends in the central configuration? For \(N=100\), what are (d) \(W\) of the central configuration, (e) the total number of microstates, and (f) the percentage of the time the system spends in the central configuration? For \(N=200\), what are (g) \(W\) of the central configuration, (h) the total number of microstates, and (i) the percentage of the time the system spends in the central configuration? (j) Does the time spent in the central configuration increase or decrease with an increase in \(N\) ?

How much energy must be transferred as heat for a reversible isothermal expansion of an ideal gas at \(132^{\circ} \mathrm{C}\) if the entropy of the gas increases by \(46.0 \mathrm{~J} / \mathrm{K} ?\)

An ideal gas undergoes a reversible isothermal expansion at \(77.0^{\circ} \mathrm{C}\), increasing its volume from \(1.30 \mathrm{~L}\) to \(3.40 \mathrm{~L}\). The entropy change of the gas is \(22.0 \mathrm{~J} / \mathrm{K}\). How many moles of gas are present?

Suppose that a deep shaft were drilled in Earth's crust near one of the poles, where the surface temperature is \(-40^{\circ} \mathrm{C}\), to a depth where the temperature is \(800^{\circ} \mathrm{C}\). (a) What is the theoretical limit to the efficiency of an engine operating between these temperatures? (b) If all the energy released as heat into the lowtemperature reservoir were used to melt ice that was initially at \(-40^{\circ} \mathrm{C}\), at what rate could liquid water at \(0^{\circ} \mathrm{C}\) be produced by a 100 MW power plant (treat it as an engine)? The specific heat of ice is \(2220 \mathrm{~J} / \mathrm{kg} \cdot \mathrm{K} ;\) water's heat of fusion is \(333 \mathrm{~kJ} / \mathrm{kg}\). (Note that the engine can operate only between \(0^{\circ} \mathrm{C}\) and \(800^{\circ} \mathrm{C}\) in this case. Energy exhausted at \(-40^{\circ} \mathrm{C}\) cannot warm anything above \(-40^{\circ} \mathrm{C}\).)

The electric motor of a heat pump transfers energy as heat from the outdoors, which is at \(-5.0^{\circ} \mathrm{C}\), to a room that is at \(17^{\circ} \mathrm{C}\). If the heat pump were a Carnot heat pump (a Carnot engine working in reverse), how much energy would be transferred as heat to the room for each joule of electric energy consumed?

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