JEE Main
Q. In the kinetic theory of gases, which of the following quantities is directly proportional to the square of the speed of gas molecules?
A.
Pressure
B.
Volume
C.
Temperature
D.
Density
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Solution
According to the kinetic theory, pressure is directly proportional to the average kinetic energy of the gas molecules, which is proportional to the square of their speed.
Correct Answer: A — Pressure
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Q. In the Langmuir adsorption isotherm, what assumption is made about the adsorption sites?
A.
They are identical and have the same energy
B.
They are different and have varying energy
C.
They can accommodate multiple layers
D.
They are not limited in number
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Solution
The Langmuir isotherm assumes that all adsorption sites are identical and have the same energy.
Correct Answer: A — They are identical and have the same energy
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Q. In the Langmuir adsorption isotherm, what does the term 'b' represent?
A.
Adsorption energy
B.
Surface area
C.
Equilibrium constant
D.
Adsorption capacity
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Solution
'b' in the Langmuir isotherm represents the equilibrium constant related to the adsorption process.
Correct Answer: C — Equilibrium constant
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Q. In the measurement 0.007890, how many significant figures are present?
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Solution
The significant figures are 7, 8, 9, and 0, totaling 4 significant figures.
Correct Answer: C — 5
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Q. In the measurement 0.03040, how many significant figures are present?
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Solution
In 0.03040, the leading zeros do not count, but the trailing zero after the decimal does. Therefore, there are 4 significant figures.
Correct Answer: B — 4
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Q. In the measurement 123.45, how many significant figures are present?
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Solution
All digits in 123.45 are significant, giving a total of 5 significant figures.
Correct Answer: C — 5
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Q. In the measurement 150.0, how many significant figures are present?
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Solution
The significant figures are 1, 5, and the trailing zero after the decimal point.
Correct Answer: C — 4
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Q. In the measurement 2500 kg, how many significant figures are there?
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Solution
The number 2500 kg has two significant figures unless specified otherwise (e.g., with a decimal point).
Correct Answer: A — 2
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Q. In the molecular orbital diagram of diatomic nitrogen (N2), which orbitals are filled first?
A.
σ2s, σ*2s
B.
σ2p, π2p
C.
π2p, σ2p
D.
σ*2p, π*2p
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Solution
In N2, the 2s orbitals (σ2s and σ*2s) are filled before the 2p orbitals.
Correct Answer: A — σ2s, σ*2s
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Q. In the molecular orbital theory, which of the following is true for the π molecular orbitals?
A.
They are formed by end-to-end overlap.
B.
They are lower in energy than σ orbitals.
C.
They can accommodate a maximum of 2 electrons.
D.
They are always bonding.
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Solution
π molecular orbitals can accommodate a maximum of 2 electrons, similar to all molecular orbitals.
Correct Answer: C — They can accommodate a maximum of 2 electrons.
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Q. In the molecular orbital theory, which of the following orbitals is lower in energy than the 2p orbitals?
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Solution
The 2s molecular orbitals are lower in energy than the 2p molecular orbitals.
Correct Answer: A — 2s
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Q. In the molecular orbital theory, which of the following orbitals is lower in energy for homonuclear diatomic molecules?
A.
σ2p
B.
π2p
C.
σ2s
D.
π2s
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Solution
The σ2s orbital is lower in energy than the π2p and σ2p orbitals in homonuclear diatomic molecules.
Correct Answer: C — σ2s
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Q. In the molecular orbital theory, which of the following orbitals is the highest energy in O2?
A.
σ2p
B.
π2p
C.
σ*2p
D.
π*2p
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Solution
The highest energy orbital in O2 is σ*2p, which is an antibonding orbital.
Correct Answer: C — σ*2p
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Q. In the molecular orbital theory, which of the following orbitals is the highest occupied molecular orbital (HOMO) in O2?
A.
σ2p
B.
π2p
C.
σ*2p
D.
π*2p
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Solution
In O2, the highest occupied molecular orbital (HOMO) is π2p.
Correct Answer: B — π2p
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Q. In the molecular orbital theory, which of the following pairs of orbitals can combine to form a sigma bond?
A.
s and p
B.
p and p
C.
s and s
D.
d and p
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Solution
s and s orbitals can combine to form a sigma bond.
Correct Answer: C — s and s
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Q. In the molecular orbital theory, which orbitals combine to form sigma bonds?
A.
s and p orbitals
B.
p and d orbitals
C.
s orbitals only
D.
p orbitals only
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Solution
Sigma bonds are formed by the head-on overlap of s and p orbitals.
Correct Answer: A — s and p orbitals
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Q. In the number 0.0004560, how many significant figures are present?
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Solution
The leading zeros are not significant, but the trailing zero is significant. Therefore, it has 4 significant figures.
Correct Answer: B — 4
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Q. In the number 0.007890, how many significant figures are there?
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Solution
The significant figures are 7, 8, 9, and the leading zeros are not counted.
Correct Answer: C — 5
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Q. In the number 2500, how many significant figures are there?
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Solution
Without a decimal point, 2500 has 2 significant figures.
Correct Answer: A — 2
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Q. In the number 4500, how many significant figures are there?
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Solution
4500 has 2 significant figures unless specified with a decimal point.
Correct Answer: A — 2
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Q. In the number 5000, how many significant figures are there?
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Solution
5000 has 1 significant figure unless specified with a decimal point (e.g., 5000.).
Correct Answer: A — 1
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Q. In the photoelectric effect, if the frequency of incident light is doubled, what happens to the kinetic energy of the emitted electrons?
A.
It doubles
B.
It quadruples
C.
It remains the same
D.
It becomes zero
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Solution
The kinetic energy of the emitted electrons is given by KE = hf - φ. If the frequency is doubled, the kinetic energy increases by a factor of four, since KE is proportional to the frequency.
Correct Answer: B — It quadruples
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Q. In the photoelectric effect, increasing the intensity of light increases the:
A.
Kinetic energy of emitted electrons
B.
Number of emitted electrons
C.
Wavelength of emitted light
D.
Work function
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Solution
Increasing the intensity of light increases the number of emitted electrons, as intensity is related to the number of photons hitting the surface.
Correct Answer: B — Number of emitted electrons
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Q. In the photoelectric effect, the kinetic energy of the emitted electrons depends on which of the following?
A.
Frequency of the incident light
B.
Intensity of the incident light
C.
Wavelength of the incident light
D.
All of the above
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Solution
The kinetic energy of the emitted electrons in the photoelectric effect depends on the frequency of the incident light, as per Einstein's photoelectric equation.
Correct Answer: A — Frequency of the incident light
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Q. In the photoelectric effect, what does the term 'work function' refer to?
A.
The energy of the incident photons
B.
The energy required to remove an electron from the metal
C.
The maximum kinetic energy of emitted electrons
D.
The frequency of the incident light
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Solution
The work function is the minimum energy required to remove an electron from the surface of a metal.
Correct Answer: B — The energy required to remove an electron from the metal
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Q. In the photoelectric effect, what does the work function represent?
A.
The energy of the incident photons
B.
The maximum kinetic energy of emitted electrons
C.
The minimum energy required to remove an electron from the metal
D.
The frequency of the incident light
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Solution
The work function is the minimum energy required to remove an electron from the surface of the metal.
Correct Answer: C — The minimum energy required to remove an electron from the metal
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Q. In the photoelectric effect, what happens to the emitted electrons if the frequency of the incident light is just at the threshold frequency?
A.
They are emitted with maximum kinetic energy
B.
They are emitted with zero kinetic energy
C.
They are not emitted
D.
They are emitted with negative kinetic energy
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Solution
At the threshold frequency, the energy of the incident photons is equal to the work function, resulting in emitted electrons having zero kinetic energy.
Correct Answer: B — They are emitted with zero kinetic energy
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Q. In the photoelectric effect, what happens to the energy of the incident photon if it exceeds the work function?
A.
All energy is used to emit electrons
B.
Excess energy becomes kinetic energy
C.
No electrons are emitted
D.
Energy is lost as heat
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Solution
The excess energy of the photon becomes the kinetic energy of the emitted photoelectrons.
Correct Answer: B — Excess energy becomes kinetic energy
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Q. In the photoelectric effect, what happens to the kinetic energy of emitted electrons if the frequency of incident light is increased?
A.
It decreases
B.
It remains constant
C.
It increases linearly with frequency
D.
It increases with the square of frequency
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Solution
The kinetic energy of emitted electrons increases linearly with the frequency of the incident light, according to the equation KE = hf - φ.
Correct Answer: C — It increases linearly with frequency
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Q. In the photoelectric effect, what happens to the kinetic energy of emitted electrons if the intensity of light is increased while keeping frequency constant?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
The kinetic energy of emitted electrons remains the same as it depends on the frequency, not intensity.
Correct Answer: C — Remains the same
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