Insulating windows. One way to improve insulation in windows is to fill a sealed space between two glass panes with a gas that has a lower thermal conductivity than that of air. The thermal conductivity k of a gas depends on its molar heat capacity C V , molar mass M , and molecular radius r . The dependence on those quantities at a given temperature is approximately k ∝ C v / r 2 M . The noble gases have properties that make them particularly good choices as insulating gases. Noble gases range from helium (molar mass 4.0 g/mol, molecular radius 0.13 nm) to xenon (molar mass 131 g/mol. molecular radius 0.22 nm), (The noble gas radon is heavier than xenon, but radon is radioactive and so is not suitable for this purpose.) 81. Give one reason why the noble gases are preferable to air (which is mostly nitrogen and oxygen) as an insulating material. A. Noble gases are monatomic, so no rotational modes contribute to their molar heat capacity. B. Noble gases are monatomic, so they have lower molecular masses than do nitrogen and oxygen. C. The molecular radii in noble gases are much larger than those of gases that consist of diatomic molecules. D. Because noble gases are monatomic, they have many more degrees of freedom than do diatomic molecules, and their molar heat capacity is reduced by the number of degrees of freedom.
Insulating windows. One way to improve insulation in windows is to fill a sealed space between two glass panes with a gas that has a lower thermal conductivity than that of air. The thermal conductivity k of a gas depends on its molar heat capacity C V , molar mass M , and molecular radius r . The dependence on those quantities at a given temperature is approximately k ∝ C v / r 2 M . The noble gases have properties that make them particularly good choices as insulating gases. Noble gases range from helium (molar mass 4.0 g/mol, molecular radius 0.13 nm) to xenon (molar mass 131 g/mol. molecular radius 0.22 nm), (The noble gas radon is heavier than xenon, but radon is radioactive and so is not suitable for this purpose.) 81. Give one reason why the noble gases are preferable to air (which is mostly nitrogen and oxygen) as an insulating material. A. Noble gases are monatomic, so no rotational modes contribute to their molar heat capacity. B. Noble gases are monatomic, so they have lower molecular masses than do nitrogen and oxygen. C. The molecular radii in noble gases are much larger than those of gases that consist of diatomic molecules. D. Because noble gases are monatomic, they have many more degrees of freedom than do diatomic molecules, and their molar heat capacity is reduced by the number of degrees of freedom.
Insulating windows. One way to improve insulation in windows is to fill a sealed space between two glass panes with a gas that has a lower thermal conductivity than that of air. The thermal conductivity k of a gas depends on its molar heat capacity CV, molar mass M, and molecular radius r. The dependence on those quantities at a given temperature is approximately k ∝ Cv/r2
M
. The noble gases have properties that make them particularly good choices as insulating gases. Noble gases range from helium (molar mass 4.0 g/mol, molecular radius 0.13 nm) to xenon (molar mass 131 g/mol. molecular radius 0.22 nm), (The noble gas radon is heavier than xenon, but radon is radioactive and so is not suitable for this purpose.)
81. Give one reason why the noble gases are preferable to air (which is mostly nitrogen and oxygen) as an insulating material.
A. Noble gases are monatomic, so no rotational modes contribute to their molar heat capacity.
B. Noble gases are monatomic, so they have lower molecular masses than do nitrogen and oxygen.
C. The molecular radii in noble gases are much larger than those of gases that consist of diatomic molecules.
D. Because noble gases are monatomic, they have many more degrees of freedom than do diatomic molecules, and their molar heat capacity is reduced by the number of degrees of freedom.
You are working in a condensed-matter laboratory for your senior project. Several of the ongoing projects use liquid helium, which is contained in a thermally insulated vessel that can hold up to a maximum of Vmax = 240 L of the liquid at Tc = 4.20 K. Because some of the liquid helium has already been used, someone asks you to check to see if there is enough for the next day, on which four different experimental groups will need liquid helium. You are not sure how to measure the amount of liquid remaining, so you insert an aluminum rod of length L = 2.00 m and with a cross-sectional area A = 2.50 cm2 into the vessel. By seeing how much of the lower end of the rod is frosted when you pull it out, you can estimate the depth of the liquid helium. After inserting the rod, however, one of the experimenters calls you over to perform a task and you forget about the rod, leaving it in the liquid helium until the next morning. How much liquid helium is available for the next day’s experiments?…
A sample of an ideal gas is in a tank of
constant volume. The sample gains heat
energy and its temperature changes from 300
K to 900 K. If v, is the average speed of the
gas molecules
before absorption of heat and v2 the average
speed after absorption of heat, what is the
ratio v2/v, ?
A 3/2
B V3
30.
D 1/3
The number density in a container of neon gas is 4.80×1025 m^−3. The atoms are moving with an rms speed of 680 m/s .
What is the pressure inside the container?
p= 2.46×105 Pa
What is the temperature inside the container? In K
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