1. A fixed amount of ideal gas is held in a rigid container that expands negligi
ID: 1514724 • Letter: 1
Question
1. A fixed amount of ideal gas is held in a rigid container that expands negligibly when heated. At 20°C the gas pressure is p. If we add enough heat to increase the temperature from 20°C to 40°C, the pressure will be
A.impossible to determine since we do not know the number of moles of gas in the container.
B.greater than 2p.
C.less than 2p.
D.equal to 2p.
E.impossible to determine since we do not know the volume of gas in the container.
2. The number of molecules in one mole of a substance
A.depends on the molecular weight of the substance.
B.depends on the atomic weight of the substance.
C.depends on the density of the substance.
D.depends on the temperature of the substance.
E.is the same for all substances.
3. The average molecular kinetic energy of a gas can be determined by knowing
A.only the number of molecules in the gas.
B.only the volume of the gas.
C.only the pressure of the gas.
D.only the temperature of the gas.
E.All of the above quantities must be known to determine the average molecular kinetic energy.
4. A sample of an ideal gas is slowly compressed to one-half its original volume with no change in pressure. If the original root-mean-square speed (thermal speed) of the gas molecules was V, the new speed is
A.V.
B.2V.
C.21/2V.
D.V/2.
E.V/21/2
5. A container is filled with a mixture of helium (light molecules) and oxygen (heavy molecules) gases. A thermometer in the container reads 22°C. Which gas molecules have the greater average speed?
A.It is the same for both of the gases because the temperatures are the same.
B.The oxygen molecules do because they are diatomic.
C.The oxygen molecules do because they are more massive.
D.The helium molecules do because they are less massive.
E.The helium molecules do because they are monatomic.
Explanation / Answer
( 1 )
In actual pressure is proportional to temperature at a constant volume,
As temperature doubled, some of heat convert in the form of internal energy ( container + gas ) , so the presssure of gas is less than 2P, not doubled.
Correct option is C.less than 2p.
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The number of molecules in one mole of a substance is the same for all substances.
Correct option is ( E )
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( 3 )
Temperature (in K) of a gas is defined as the average kinetic energy of the molecules
Correct option : ( D )
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( 4 )
If the original root-mean-square speed (thermal speed) of the gas molecules was V, the new speed is
v / sqrt ( 2)
correct option is ( E )
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( 5)
In this case, the helium molecules do because they are less massive
Correct option : ( D )
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