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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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Step 1: Identify the initial conditions of the gas. Here, the initial number of moles (n) is 0.100 mol, initial pressure (P1) is 1.00 * 10^5 Pa, and initial volume (V1) is 2.50 * 10^-3 m^3.
Step 2: Calculate the final volume (V2) after expansion. Since the volume is doubled, V2 = 2 * V1.
Step 3: For isothermal expansion (i), use the ideal gas law, PV = nRT, where T remains constant. Since the temperature is constant, the final pressure can be found using P1V1 = P2V2, solving for P2.
Step 4: For isobaric expansion (ii), the pressure remains constant (P2 = P1). Use the ideal gas law to find the final temperature by setting up the equation nRT1/V1 = nRT2/V2 and solving for T2.
Step 5: For adiabatic expansion (iii), use the adiabatic condition PV^gamma = constant, where gamma (γ) for a monatomic gas is 5/3. Use this relation along with the initial conditions to find the final pressure and temperature. You can use P1V1^gamma = P2V2^gamma to find P2, and then use the ideal gas law to find T2.

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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 Kelvin. This law is fundamental for understanding how gases behave under different conditions, especially during expansions and compressions.
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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 type of process affects the gas's temperature and pressure differently during expansion. Understanding these processes is crucial for predicting the behavior of the gas when it undergoes changes in volume.
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Monatomic Ideal Gas Properties

Monatomic ideal gases consist of single atoms and exhibit specific heat capacities that differ from diatomic or polyatomic gases. For a monatomic gas, 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 calculating temperature changes and pressures during various thermodynamic processes.
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Related Practice
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.)
798
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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.
417
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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
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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Textbook Question
Five moles of an ideal monatomic gas with an initial temperature of 127°C expand and, in the process, absorb 1500 J of heat and do 2100 J of work. What is the final temperature of the gas?
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