Ncert Solutions Chemistry Class 11th
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Threshold frequency, ν0 is the minimum frequency which a photon must possess to eject an electron from a metal. It is different for different metals. When a photon of frequency 1.0×1015 s–1 was allowed to hit a metal surface, an electron having 1.988 × 10–19 J of kinetic energy was emitted. Calculate the threshold frequency of this metal. Show that an electron will not be emitted if a photon with a wavelength equal to 600 nm hits the metal surface.
Threshold frequency, ν0 is the minimum frequency which a photon must possess to eject an electron from a metal. It is different for different metals. When a photon of frequency 1.0×1015 s–1 was allowed to hit a metal surface, an electron having 1.988 × 10–19 J of kinetic energy was emitted. Calculate the threshold frequency of this metal. Show that an electron will not be emitted if a photon with a wavelength equal to 600 nm hits the metal surface.
This is a Long Answer Type Questions as classified in NCERT Exemplar
ANS- For the emission of electrons from metal the frequency of the striking light should be higher than that of its threshold frequency. We have
h ν = hν 0 + K.E
ν 0 = ν - K.E/h ……. (1)
Given
ν = 1015 s -1, K.E = 1.988 X 10-19J
Thu
Upvote 
What is photoelectric effect? State the result of photoelectric effect experiment that could not be explained on the basis of laws of classical physics. Explain this effect on the basis of quantum theory of electromagnetic radiations.
What is photoelectric effect? State the result of photoelectric effect experiment that could not be explained on the basis of laws of classical physics. Explain this effect on the basis of quantum theory of electromagnetic radiations.
This is a Long Answer Type Questions as classified in NCERT Exemplar
ANS-When the beam of light gets exposed to the metal surface then the electrons get emitted from the metal. This effect is said to be photoelectric effect and the emitted electrons are said to be photoelectrons. The result of photoe
Upvote Electronic configuration of some elements is given in Column I and their electron gain enthalpies are given in Column II. Match the electronic configuration with electron gain enthalpy.
Column (I)
Column (II)
Electronic configuration
Electron gain enthalpy/kJ mol–1
(i) 1s2 2s2 sp6
(A) – 53
(ii) 1s2 2s2 2p6 3s1
(B) – 328
(iii) 1s2 2s2 2p5
(C) – 141
(iv) 1s2 2s2 2p4
(D) + 48
Electronic configuration of some elements is given in Column I and their electron gain enthalpies are given in Column II. Match the electronic configuration with electron gain enthalpy.
|
Column (I) |
Column (II) |
|
Electronic configuration |
Electron gain enthalpy/kJ mol–1 |
|
(i) 1s2 2s2 sp6 |
(A) – 53 |
|
(ii) 1s2 2s2 2p6 3s1 |
(B) – 328 |
|
(iii) 1s2 2s2 2p5 |
(C) – 141 |
|
(iv) 1s2 2s2 2p4 |
(D) + 48 |
This is a Matching Type Questions as classified in NCERT Exemplar
i
Upvote Match the correct ionisation enthalpies and electron gain enthalpies of the following elements.
Elements
?H1
? H2
?egH
(i) Most reactive non metal
A
419
3051
– 48
(ii) Most reactive metal
B
i b
i b
i b
(iii) Least reactive element
C
738
1451
– 40
(iv) Metal forming binary halide
D
2372
5251
+ 48
Match the correct ionisation enthalpies and electron gain enthalpies of the following elements.
|
Elements |
|
?H1 |
? H2 |
?egH |
|
(i) Most reactive non metal |
A |
419 |
3051 |
– 48 |
|
(ii) Most reactive metal |
B |
i b |
i b |
i b |
|
(iii) Least reactive element |
C |
738 |
1451 |
– 40 |
|
(iv) Metal forming binary halide |
D |
2372 |
5251 |
+ 48 |
This is a Matching Type Questions as classified in NCERT Exemplar
i ) b 1681 3374 – 328
ii )
Upvote Match the correct atomic radius with the element.
Element
Atomic Radius (pm)
Be
74
C
88
O
111
B
77
N
66
Match the correct atomic radius with the element.
|
Element |
Atomic Radius (pm) |
|
Be |
74 |
|
C |
88 |
|
O |
111 |
|
B |
77 |
|
N |
66 |
This is a Matching Type Questions as classified in NCERT Exemplar
Be
Upvote Assertion (A) : Electron gain enthalpy becomes less negative as we go down a group.
Reason (R) : Size of the atom increases on going down the group and the added electron would be farther from the nucleus.
(i) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(ii) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(iii) Assertion and reason both are wrong statements.
(iv) Assertion is wrong statement but reason is correct statement.
Assertion (A) : Electron gain enthalpy becomes less negative as we go down a group.
Reason (R) : Size of the atom increases on going down the group and the added electron would be farther from the nucleus.
(i) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(ii) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(iii) Assertion and reason both are wrong statements.
(iv) Assertion is wrong statement but reason is correct statement.
This is a Assertion and Reason Type Questions as classified in NCERT Exemplar
Option (ii)
The electron gain enthalpy decreases down the group due to the increase in the atomic size which leads to decrease in the effective nuclear charge.
Upvote Assertion (A) : Boron has a smaller first ionisation enthalpy than beryllium.
Reason (R) : The penetration of a 2s electron to the nucleus is more than the 2p electron hence 2p electron is more shielded by the inner core of electrons than the 2s electrons.
(i) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(ii) Assertion is correct statement but reason is wrong statement.
(iii) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(iv) Assertion and reason both are wrong statements
Assertion (A) : Boron has a smaller first ionisation enthalpy than beryllium.
Reason (R) : The penetration of a 2s electron to the nucleus is more than the 2p electron hence 2p electron is more shielded by the inner core of electrons than the 2s electrons.
(i) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(ii) Assertion is correct statement but reason is wrong statement.
(iii) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(iv) Assertion and reason both are wrong statements
This is a Assertion and Reason Type Questions as classified in NCERT Exemplar
Option (iii)
The Be has the electronic configuration of [He]2s2 while B has the electronic configuration of [He]2s22p1 . As in Be the outermost orbital i.e. 2s is fully filled thus it provides extra stability to the Be compa
Upvote In the following questions a statement of Assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.
Assertion (A) : Generally, ionisation enthalpy increases from left to right in a period.
Reason (R) : When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate.
(i) Assertion is correct statement and reason is wrong statement.
(ii) Assertion and reason both are correct statements and reason is correct explanation of assertion.
(iii) Assertion and reason both are wrong statements.
(iv) Assertion is wrong statement and reason is correct statement.
In the following questions a statement of Assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.
Assertion (A) : Generally, ionisation enthalpy increases from left to right in a period.
Reason (R) : When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate.
(i) Assertion is correct statement and reason is wrong statement.
(ii) Assertion and reason both are correct statements and reason is correct explanation of assertion.
(iii) Assertion and reason both are wrong statements.
(iv) Assertion is wrong statement and reason is correct statement.
This is a Assertion and Reason Type Questions as classified in NCERT Exemplar
Option (ii)
The ionization energy depends upon two factors
(a) The effective nuclear charge.
(b)The e- -e – repulsions.
Upvote An element belongs to 3rd period and group-13 of the periodic table. Which of the following properties will be shown by the element?
(i) Good conductor of electricity
(ii) Liquid, metallic
(iii) Solid, metallic
(iv) Solid, non metallic
An element belongs to 3rd period and group-13 of the periodic table. Which of the following properties will be shown by the element?
(i) Good conductor of electricity
(ii) Liquid, metallic
(iii) Solid, metallic
(iv) Solid, non metallic
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (i)& (iii)
Aluminium is the element which is a metal and good conductor of electricity.
Upvote