/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 33 We have two equal-size boxes, \(... [FREE SOLUTION] | 91Ó°ÊÓ

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We have two equal-size boxes, \(A\) and \(B\) . Each box contains gas that behaves as an ideal gas. We insert a thermometer into each box and find that the gas in box \(A\) is at a temperature of \(50^{\circ} \mathrm{C}\) while the gas in box \(B\) is at \(10^{\circ} \mathrm{C}\) . This is all we know about the gas in the boxes. Which of the following statements must be true? Which could be true? (a) The pressure in \(A\) is higher than in \(B\) . There are more molecules in \(A\) than in \(B .(\mathrm{c}) A\) and \(B\) cannot contain the same type of gas. (d) The molecules in \(A\) have more average kinetic energy per molecule than those in \(B\) . (e) The molecules in \(A\) are moving faster than those in \(B\) . Explain the reasoning behind your answers.

Short Answer

Expert verified
Statement (d) must be true; statements (a) and (e) could be true.

Step by step solution

01

Understanding Ideal Gas Concept

The ideal gas law is given as \( PV = nRT \), where \( P \) is the pressure, \( V \) is the volume, \( n \) is the number of moles, \( R \) is the ideal gas constant, and \( T \) is the temperature in Kelvin. A relationship between temperature and kinetic energy is given by \( KE = \frac{3}{2}kT \), where \( k \) is the Boltzmann constant.
02

Convert Temperatures to Kelvin

The Celsius temperatures need to be converted to Kelvin to understand the kinetic energy and temperature relation accurately. \[ T_A = 50^{\circ}C + 273 = 323K \] \[ T_B = 10^{\circ}C + 273 = 283K \]
03

Analyze Pressure (Statement a)

Since \(V\) and \(R\) are constant for both boxes, if \(n\) is also constant, then \( P \propto T \). Thus, \( P_A > P_B \) because \( T_A > T_B \). However, this assumes equal moles which are not stated, so pressure in \(A\) being higher is not necessarily true without additional information.
04

Compare Number of Molecules (Statement b)

The number of molecules depends on the number of moles \(n\). Without specific information about the moles of gas or their type, we cannot determine if \(A\) has more molecules than \(B\). Therefore, this is not necessarily true.
05

Determine Gas Type (Statement c)

The type of gas cannot be determined from temperature alone. Two different gases might have the same temperature and pressure conditions but differ in molecular properties. Therefore, \(A\) and \(B\) could contain the same type of gas; hence it is not necessarily true they cannot contain the same gas.
06

Calculate Average Kinetic Energy (Statement d)

Average kinetic energy per molecule is directly proportional to the temperature in Kelvin. Since \( T_A > T_B \), the average kinetic energy of molecules in \(A\) is higher than in \(B\). Statement (d) must be true.
07

Compare Molecular Speeds (Statement e)

The speed of molecules is related to their kinetic energy as \( v = \sqrt{\frac{3kT}{m}} \). While temperature implies greater energy, the direct comparison of speeds also depends on the mass \( m \). Assuming similar gas types or approximating mass as a constant, molecules in \(A\) are moving faster than those in \(B\). Thus, statement (e) could be true.

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Key Concepts

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

Temperature Conversion
Temperature is a fundamental aspect of thermodynamics and plays a key role in understanding gas behavior. In this exercise, the temperatures of gases are given in degrees Celsius, a common unit of temperature. However, for calculations involving the Ideal Gas Law, we must convert these temperatures to Kelvin. This is because Kelvin is the standard SI unit of temperature, starting from absolute zero, which makes mathematical manipulation involving temperature more accurate and meaningful.
To convert from Celsius to Kelvin, you add 273 to the Celsius temperature. The conversion formula is:
  • For box A: \(T_A = 50^{\circ}C + 273 = 323 K\)
  • For box B: \(T_B = 10^{\circ}C + 273 = 283 K\)
This conversion is crucial because it allows us to use the temperature to determine other properties of the gas, like kinetic energy and molecular speed.
Kinetic Energy
Kinetic energy in the context of gases is an indicator of how energetically the molecules in the gas are moving. It directly relates to the temperature of the gas, and can be described by the formula \( KE = \frac{3}{2}kT \). Here, \( k \) is the Boltzmann constant and \( T \) is the temperature in Kelvin.
The formula illustrates that kinetic energy is directly proportional to temperature. Therefore, an increase in the temperature of a gas leads to an increase in the average kinetic energy of its molecules. In the given exercise, since box A has a higher temperature than box B after conversion to Kelvin, we can conclude:
  • The average kinetic energy of molecules in box A is higher than in box B.
  • Statement (d) in the exercise is thus true because temperature \(T_A\) is greater than \(T_B\).
Understanding this relationship is crucial for analyzing the energetic dynamics of gas molecules and their behaviors under different temperature conditions.
Molecular Speed
The speed of molecules in a gas is another important factor to consider when determining the physical state and behavior of the gas. Molecular speed is linked with kinetic energy and mass by the equation \( v = \sqrt{\frac{3kT}{m}} \). This provides the root-mean-square speed of molecules, where \( m \) represents the molecular mass.
In our scenario, since temperature \( T \) is greater in box A, the kinetic energy and speed of molecules could be higher if the gas type (and thus molecular mass) remains constant between the boxes. Key points include:
  • Molecules in box A might move faster than in box B, provided their masses are similar.
  • Therefore, statement (e) could be true, based on these assumptions.
It’s essential to understand that while temperature gives us insights into probable speeds, actual molecular speed depends also on the molecule’s mass, so assumptions need validation with more data.

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Most popular questions from this chapter

Helium gas with a volume of 2.60 \(\mathrm{L}\) , under a pressure of 1.30 atm and at a temperanure of \(41.0^{\circ} \mathrm{C},\) is warmed until both pressure and volume are doubled. (a) What is the final temperature? (b) How many grams of helium are there? The molar mass of helium is 4.00 \(\mathrm{g} / \mathrm{mol.}\)

Atmosphere of Titan. Titan, the largest satellite of Saturn, has a thick nitrogen atmosphere. At its surface, the pressure is 1.5 Earth-atmospheres and the temperature is 94 \(\mathrm{K}\) . (a) What is the surface temperature in \(^{\circ} \mathrm{C}\) ? (b) Calculate the surface density in Titar's atmosphere in molecules per cubic meter (c) Compare the density of Titan's surface atmosphere to the density of Earth's atmosphere at \(22^{\circ} \mathrm{C}\) . Which body has denser atmosphere?

A cylindrical tank has a tight-fitting piston that allows the volume of the tank to be changed. The tank originally contains 0.110 \(\mathrm{m}^{3}\) of air at pressure of 3.40 atm. The piston is slowly pulled out until the volume of the gas is increased to 0.390 \(\mathrm{m}^{3} .\) If the temperature remains constant, what is the final value of the pressure?

For carbon dioxide gas \(\left(\mathrm{CO}_{2}\right),\) the constants in the van der Waals equation are \(a=0.364 \mathrm{J} \cdot \mathrm{m}^{3} / \mathrm{mol}^{2}\) and \(b=4.27 \times 10^{-5} \mathrm{m}^{3} / \mathrm{mol} .\) (a) If 1.00 \(\mathrm{mol}\) of \(\mathrm{CO}_{2} \mathrm{gas}\) at 350 \(\mathrm{K}\) is confined to a volume of 400 \(\mathrm{cm}^{3}\) , find the pressure of the gas using the ideal-gas equation and the van der Waals equation. (b) Which equation gives a lower pressure? Why? What is the percentage difference of the van der Waals equation result from the ideat-gas equation result? (c) The gas is kept at the same temperature as it expands to a volume of 4000 \(\mathrm{cm}^{3} .\) Repeat the calculations of parts (a) and (b). (d) Explain how your calculations show that the van der Waals equation is equivalent to the ideat-gas equation if \(n / V\) is small.

Modern vacuum pumps make it easy to attain pressures of the order of \(10^{-13}\) atm in the laboratory. (a) At a pressure of \(9.00 \times 10^{-14}\) am and an ordinary temperature of \(300.0 \mathrm{K},\) how many inolecules are present in a volume of 1.00 \(\mathrm{cm}^{3} ?\) (b) How many molecules would be present at the same temperature but at 1.00 atm instead?

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