Chapter 1: Problem 32
Derive an expression for the compression factor of a gas that obeys the equation of state \(p(V-n b)=n R T\), where \(b\) and \(R\) are constants. If the pressure and temperature are such that \(V_{m}=10 b\), what is the numerical value of the compression factor?
Short Answer
Expert verified
\( Z = \frac{10}{9} \)
Step by step solution
01
Define the Compression Factor
The compression factor, also known as the Z-factor, is defined as the ratio of the molar volume of a gas to the molar volume of an ideal gas at the same temperature and pressure. It can be expressed as: \( Z = \frac{pV_m}{nRT} \).
02
Rearrange the Given Equation of State
From the given equation of state \( p(V - n b) = nRT \), we rearrange it to express \( V_m \), the molar volume: \( V_m = \frac{V}{n} = \frac{RT}{p} + b \).
03
Substitute Expression for Molar Volume in Compression Factor
Substitute the expression for \( V_m \) into the formula for \( Z \) which gives: \( Z = \frac{p(\frac{RT}{p} + b)}{nRT} = \frac{pRT}{nRT} + \frac{pb}{nRT} = 1 + \frac{pb}{RT} \).
04
Find Molar Volume Under Given Conditions
Under the given conditions where \( V_m = 10b \), we need to find the numerical value of the compression factor.
05
Calculate the Numerical Value of Compression Factor
Substitute \( V_m = 10b \) into the expression for \( Z \): \( Z = 1 + \frac{pb}{RT} \). Since \( V_m \) is 10 times \( b \), and \( V_m = \frac{RT}{p} + b \), this means that \( \frac{RT}{p} = 9b \). Now, we can substitute \( \frac{RT}{p} \) with \( 9b \) in the equation for \( Z \) to get \( Z = 1 + \frac{p \cdot b}{9b \cdot R} \). Simplifying this, we have \( Z = 1 + \frac{1}{9} \), therefore \( Z = \frac{10}{9} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Equation of State
In physical chemistry, an equation of state is a mathematical model that describes the state of matter under a given set of physical conditions. It provides a relationship between various state functions such as pressure (p), volume (V), temperature (T), and the amount of substance (n) in moles. This relation helps scientists and engineers predict the behavior of gases and liquids with varying degrees of accuracy.
One of the simplest forms is the Ideal Gas Law, expressed as \(pV=nRT\), where R is the universal gas constant. However, real gases deviate from ideal behavior due to particle volume and intermolecular forces. The Van der Waals equation is an example of a more complex equation of state that corrects for these factors. In the given exercise, the equation of state \(p(V-nb)=nRT\) accounts for volume exclusions by subtracting \(nb\), where \(b\) is a constant representing the volume occupied by one mole of gas molecules.
By understanding equations of state, you can derive important properties of gases, including the compression factor - a measure of how much a gas deviates from ideal behavior as given in the exercise solution.
One of the simplest forms is the Ideal Gas Law, expressed as \(pV=nRT\), where R is the universal gas constant. However, real gases deviate from ideal behavior due to particle volume and intermolecular forces. The Van der Waals equation is an example of a more complex equation of state that corrects for these factors. In the given exercise, the equation of state \(p(V-nb)=nRT\) accounts for volume exclusions by subtracting \(nb\), where \(b\) is a constant representing the volume occupied by one mole of gas molecules.
By understanding equations of state, you can derive important properties of gases, including the compression factor - a measure of how much a gas deviates from ideal behavior as given in the exercise solution.
Molar Volume
The concept of molar volume is central to understanding the properties of substances in their gaseous state. Molar volume, represented as \(V_m\), is the volume occupied by one mole of a substance at a given temperature and pressure. It's a vital bridge tying together the microscopic world with macroscopic measurements, allowing chemists to convert between the amount of substance (in moles) and the volume it occupies.
For an ideal gas, the molar volume can be obtained directly using the ideal gas equation, but for real gases, adjustments must be made. The step-by-step solution in the exercise above demonstrates how to rearrange the provided equation of state to express molar volume. This process illustrates the adaptability of molar volume calculations to account for non-ideal behavior captured within modified equations of state, thus enabling a deeper understanding of the gas under study.
For an ideal gas, the molar volume can be obtained directly using the ideal gas equation, but for real gases, adjustments must be made. The step-by-step solution in the exercise above demonstrates how to rearrange the provided equation of state to express molar volume. This process illustrates the adaptability of molar volume calculations to account for non-ideal behavior captured within modified equations of state, thus enabling a deeper understanding of the gas under study.
Physical Chemistry
Physical chemistry is the branch of chemistry that focuses on understanding the physical properties of molecules, the forces that act upon them, and the energy changes that occur during chemical reactions. It combines principles from physics and chemistry to explain how chemical systems behave and to predict new combinations and states of matter.
The study of physical chemistry includes thermodynamics, kinetics, molecular structure, spectroscopy, and statistical mechanics. It can explain phenomena like the compression factor in gaseous behavior, phase changes, reaction rates, and equilibrium constants. By applying mathematical models and laws, such as the equation of state discussed in the exercise, physical chemists can predict how substances will act under various conditions, which is crucial in a diverse array of applications from materials science to pharmacology.
The study of physical chemistry includes thermodynamics, kinetics, molecular structure, spectroscopy, and statistical mechanics. It can explain phenomena like the compression factor in gaseous behavior, phase changes, reaction rates, and equilibrium constants. By applying mathematical models and laws, such as the equation of state discussed in the exercise, physical chemists can predict how substances will act under various conditions, which is crucial in a diverse array of applications from materials science to pharmacology.