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Ch.6 - Gases
Chapter 6, Problem 128

A quantity of N2 occupies a volume of 1.0 L at 300 K and 1.0 atm. The gas expands to a volume of 3.0 L as the result of a change in both temperature and pressure. Find the density of the gas at these new conditions.

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Identify the initial conditions: Volume (V1) = 1.0 L, Temperature (T1) = 300 K, Pressure (P1) = 1.0 atm.
Identify the final conditions: Volume (V2) = 3.0 L. The final temperature (T2) and pressure (P2) are not given, but we need to find the density at these conditions.
Use the ideal gas law in the form \( PV = nRT \) to express the number of moles \( n \) in terms of the initial conditions: \( n = \frac{P1 \times V1}{R \times T1} \).
Assume the number of moles \( n \) remains constant. Use the ideal gas law again for the final conditions: \( P2 \times V2 = n \times R \times T2 \).
Density \( \rho \) is defined as mass per unit volume. Use the molar mass of \( N_2 \) and the number of moles \( n \) to find the mass, then divide by the final volume \( V2 \) to find the density: \( \rho = \frac{n \times \text{molar mass of } N_2}{V2} \).

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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 a gas through the equation PV = nRT. This law is fundamental for understanding gas behavior under varying conditions and allows for the calculation of one variable when the others are known.
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Density of a Gas

Density is defined as mass per unit volume. For gases, density can be calculated using the formula ρ = PM/RT, where ρ is density, P is pressure, M is molar mass, R is the ideal gas constant, and T is temperature. Understanding this relationship is crucial for determining the density of gases under different conditions.
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Changes in State Variables

When a gas undergoes changes in volume, temperature, or pressure, its state variables are interrelated. Understanding how these variables affect each other is essential for solving problems involving gas expansion or compression, as it allows for the application of the Ideal Gas Law to find unknown quantities.
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Related Practice
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