11th Class Chemistry Chapter five Short Questions with Answers Solved

Question: 1

Whichever gas is used in the discharge tube, the nature of the cathode rays remains the same. Why?

Answer: 1

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All the gases are consisted of atoms or molecules. They have electrons in outermost orbitals. These electrons are detached by the high voltage and due to collisions, these electrons become free. They are repelled by the cathode and attracted towards the anode. That is why, they are called cathode rays. They are always electrons and nothing else.

Question: 2

What is Zeeman effect?

Answer: 2

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When the light of spectral lines is passed through the magnetic field, then the one spectra line is splitted up into many spectra lines. This splitting of the spectral line cannot be explained by Bohr's theory.

Question: 3

The energy difference between adjacent levels goes on decreasing sharply. Why?

Answer: 3

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If we put the value of n as 1,2,3,4 we get the energies of various orbits of hydrogen atom. These values are as follows:

E₁= -2.18 x 10^-18J

E₂= -0.54 x 10^-18J

E₃ = -0.24 x 10^-18J

E₄ = -0.14 x 10^-18J

As is clear from these values that energy differences between adjacent levels go on decreasing from lower to the higher level.

Question: 4

Why the photographic plate is white and few dark lines are there in the line absorption spectra of a substance?

Answer: 4

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Some of the photons are absorbed by the sample to excite the electrons of and substance from lower energy levels to higher energy levels. These photons of light don't reach the photographic plate. Rest of the light reaches the photographic plate, arid the plate is white. Only those places are dark in the form of sharp lines where the photon don't reach.

Question: 5

Energy of an electron is inversely proportional to but energy of higher orbits are always greater than those of the lower orbits. Why?

Answer: 5

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Question: 6

Why the anode rays depend upon the nature of the gas?

Answer: 6

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Anode rays are those particles which are consisted of rest of the atom or molecule after the removal of one electron, the mass of every anode ray particle depends upon the nature of the gas, so the anode rays for all gaseous substances are different.

Question: 7

Why every series of H-spectrum is a convergent series?

Answer: 7

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The lines of the every series of H-spectrum are not equally spaced. The reason is that energy levels are not equally spaced. Energy levels become close to each other from lower to the higher levels. For this reason, the lines start coming close to each other. The non-equivalent energy differences make the convergent series.

Question: 8

How do you come to know that the velocities of electrons in higher orbits are less than those in lower orbits of hydrogen atom?

Answer: 8

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Question: 9

How did Rutherford's model of an atom first of all proved the existence of nucleus of the atom?

Answer: 9

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Rutherford observed that most of the a-particles passed straight through the gold foil without any deflection from the path. Few of them were deflected at some angle more than 90° and a few were deflected back on the original path. He concluded that the atom contains heavy and positively charged part at the center. This heavy part at the center is called nucleus.

Question: 10

What are defects of Bohr's atomic model?

Answer: 10

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Question: 11

How the slow neutrons prove to be more effective than the fast neutrons?

Answer: 11

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Question: 12

What is Moseley's law?

Answer: 12

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Question: 13

How the energy of the plioton can be calculated from the measurement of the frequency,
wavelength or wave number of the photon?

Answer: 13

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Question: 14

How does Bohr introduce the Planck's quantum theory in his model?

Answer: 14

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Bohr proposed that electrons move around the nucleus in the fixed orbits with definite energies. Whenever, they change the orbits they emit or absorb the energy in terms of photons which was suggested by Planck.

Question: 15

What is the function of principal quantum number?

Answer: 15

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Its values are whole numbers and never zero, negative or fractional. It gives us information about:

(i) Energy of electron.

(ii) Distance of electron from the nucleus.

Question: 16

The x-rays produced in a discharge tube experiment are characteristic of the target metal. Justify it.

Answer: 16

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The x-rays which are emitted from the surface of the metal depend upon the atomic number of the metal. Greater the number of protons in the nucleus of metal atom great the forces of attractions for the Inner electrons. Greater the energy differences, smaller the wavelength of x-rays.

Question: 17

How the value of the Redberg's constant can be justified from Bohr's equation?

Answer: 17

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Question: 18

According to Bohr's model, the angular momentum of moving electron is a quantized. Justify it.

Answer: 18

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Question: 19

State Pauli's exclusion principle and Hund's rule?

Answer: 19

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According to Pauli's principle "no two electrons in an atom can have the same set of four quantum numbers". According to Hund's rule,"if degenerate orbitals are available and more than two electrons are to be placed in them, then place them in separate orbitals with the same spins rather than in the same orbital with the opposite spins."

Question: 20

How do you prove that the energy associated with the electron which is revolving around the nucleus of H-atom is negative?

Answer: 20

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Question: 21

The magnetic quantum number gives us the orientation of orbital in space. Justify it.

Answer: 21

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In order to designate the directions of p-orbitals in p-subshell, we need an additional quantum number and that is called magnetic quantum number. It tells us the orientation of orbital in space p-subshell has three orbital and thus have three directions in space. For each direction there is a separate value of magnetic quantum number.

Question: 22

Heisenberg's uncertainty principle has no relation with Bohr's atomic model. Justify it.

Answer: 22

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Since the electron has wavy nature and paths are elliptical as well, so the simultaneous determination of position and momentum is not possible. But Bohr's model does not accommodate the wavy nature of electron. He says that the paths are fixed orbits and their orbits are planar. It means that Bohr's model is very simple as compared to Heisenberg's uncertainty principle.

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11th Class Chapter five Chemistry Short Questions

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