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Ch 19: The First Law of Thermodynamics
Chapter 19, Problem 19

A cylinder contains 0.100 mol of an ideal monatomic gas. Initially the gas is at 1.00 * 10^5 Pa and occupies a volume of 2.50 * 10^-3 m^3. (b) If the gas is allowed to expand to twice the initial volume, find the final temperature (in kelvins) and pressure of the gas if the expansion is (i) isothermal; (ii) isobaric; (iii) adiabatic.

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Identify the initial conditions of the gas: number of moles (n = 0.100 mol), initial pressure (P1 = 1.00 * 10^5 Pa), and initial volume (V1 = 2.50 * 10^-3 m^3).
Calculate the initial temperature (T1) using the ideal gas law, PV = nRT, where R is the ideal gas constant (8.314 J/(mol*K)).
For isothermal expansion (i), use the fact that temperature remains constant (T2 = T1). Apply the ideal gas law to find the final pressure (P2) after the volume has doubled (V2 = 2 * V1).
For isobaric expansion (ii), the pressure remains constant (P2 = P1). Calculate the final temperature (T2) using the relation from the ideal gas law, considering the volume has doubled (V2 = 2 * V1).
For adiabatic expansion (iii), use the adiabatic condition where PV^gamma = constant (gamma = 5/3 for monatomic gas). Calculate the final temperature (T2) and pressure (P2) using the relations T2 = T1 * (V1/V2)^(gamma-1) and P2 = P1 * (V1/V2)^gamma.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ideal Gas Law

The Ideal Gas Law relates the pressure, volume, temperature, and number of moles of an ideal gas through the equation PV = nRT. Here, P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature in kelvins. This law is fundamental for understanding how changes in one property affect the others in gas behavior.
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Types of Thermodynamic Processes

Thermodynamic processes can be classified into isothermal (constant temperature), isobaric (constant pressure), and adiabatic (no heat exchange). Each process has distinct characteristics that affect how a gas behaves when it expands or contracts. Understanding these processes is crucial for calculating changes in temperature and pressure during gas expansion.
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Monatomic Ideal Gas Properties

Monatomic ideal gases, such as helium or neon, consist of single atoms and exhibit specific heat capacities that differ from diatomic or polyatomic gases. For monatomic gases, the molar specific heat at constant volume (Cv) is 3/2 R, and at constant pressure (Cp) is 5/2 R. These properties are essential for determining temperature changes during various thermodynamic processes.
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Related Practice
Textbook Question
The engine of a Ferrari F355 F1 sports car takes in air at 20.0°C and 1.00 atm and compresses it adiabatically to 0.0900 times the original volume. The air may be treated as an ideal gas with g = 1.40. (b) Find the final temperature and pressure.
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Textbook Question
A player bounces a basketball on the floor, compressing it to 80.0% of its original volume. The air (assume it is essentially N2 gas) inside the ball is originally at 20.0°C and 2.00 atm. The ball's inside diameter is 23.9 cm. (a) What temperature does the air in the ball reach at its maximum compression? Assume the compression is adiabatic and treat the gas as ideal.
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Textbook Question
On a warm summer day, a large mass of air (atmospheric pressure 1.01 * 10^5 Pa) is heated by the ground to 26.0°C and then begins to rise through the cooler surrounding air. (This can be treated approximately as an adiabatic process; why?) Calculate the temperature of the air mass when it has risen to a level at which atmospheric pressure is only 0.850 * 105 Pa. Assume that air is an ideal gas, with g = 1.40. (This rate of cooling for dry, rising air, corresponding to roughly 1 C° per 100 m of altitude, is called the dry adiabatic lapse rate.)
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Textbook Question
A cylinder contains 0.100 mol of an ideal monatomic gas. Initially the gas is at 1.00 * 10^5 Pa and occupies a volume of 2.50 * 10^-3 m^3. (b) If the gas is allowed to expand to twice the initial volume, find the final temperature (in kelvins) and pressure of the gas if the expansion is (i) isothermal; (ii) isobaric; (iii) adiabatic.
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Textbook Question
A cylinder contains 0.100 mol of an ideal monatomic gas. Initially the gas is at 1.00 * 10^5 Pa and occupies a volume of 2.50 * 10^-3 m^3. (b) If the gas is allowed to expand to twice the initial volume, find the final temperature (in kelvins) and pressure of the gas if the expansion is (i) isothermal; (ii) isobaric; (iii) adiabatic.
506
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Textbook Question
Work Done in a Cyclic Process. (a) In Fig. 19.7a, consider the closed loop 1 → 3 → 2 → 4 → 1. This is a cyclic process in which the initial and final states are the same. Find the total work done by the system in this cyclic process, and show that it is equal to the area enclosed by the loop.

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