71.
An $$ion$$ has 18 electrons in the outermost shell, it is A
$$C{u^ + }$$
B
$$T{h^{4 + }}$$
C
$$C{s^ + }$$
D
$${K^ + }$$
Answer :
$$C{u^ + }$$
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The electronic configuration of $$Cu,Th,Cs$$ and $$K$$ are
72.
The number of electrons which will together weigh one gram is A
$$1.098 \times {10^{27}}\,{\text{electrons}}$$
B
$$9.1096 \times {10^{31}}\,{\text{electrons}}$$
C
$${\text{1}}\,\,{\text{electron}}$$
D
$$1 \times {10^4}\,{\text{electrons}}$$
Answer :
$$1.098 \times {10^{27}}\,{\text{electrons}}$$
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$$\eqalign{
& {\text{Mass of an electron}} = 9.1096 \times {10^{ - 31}}\,kg \cr
& 1\,g\,\,{\text{or}}\,\,{10^{ - 3}}\,kg = \frac{1}{{9.1096 \times {{10}^{ - 31}}}} \times {10^{ - 3}} \cr
& = 1.098 \times {10^{27}}\,{\text{electrons}} \cr} $$
73.
Which of the following configurations does not follow Hund's rule of maximum multiplicity ? A
$$1{s^2}2{s^2}2{p^6}3{s^2}3{p^2}$$
B
$$1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^6}$$
C
$$1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^1}3{d^5}$$
D
$$1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^4}4{s^2}$$
Answer :
$$1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^4}4{s^2}$$
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The configuration does not follow Hund's rule of maximum multiplicity.
74.
Maximum number of electrons in a subshell of an atom is determined by the following A
$$4l + 2$$
B
$$2l + 1$$
C
$$4l - 2$$
D
$$2{n^2}$$
Answer :
$$4l + 2$$
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Total number of subshells $$ = \left( {2l + 1} \right)$$
75.
The de Broglie wavelength of a car of mass $$1000\,kg$$ and velocity $$36\,km/hr$$ is : A
$$6.626 \times {10^{ - 34}}m$$
B
$$6.626 \times {10^{ - 38}}m$$
C
$$6.626 \times {10^{ - 31}}m$$
D
$$6.626 \times {10^{ - 30}}m$$
Answer :
$$6.626 \times {10^{ - 38}}m$$
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$$\eqalign{
& \lambda = \frac{h}{{mv}} \cr
& h = 6.6 \times {10^{ - 34}}J{\text{ - }}s \cr
& m = 1000\,kg \cr
& v = 36\,km/hr = \frac{{36 \times {{10}^3}}}{{60 \times 60}}m/\sec = 10\,m/\sec \cr
& \therefore \,\,\lambda = \frac{{6.6 \times {{10}^{ - 34}}}}{{{{10}^3} \times 10}} = 6.6 \times {10^{ - 38}}m \cr} $$
76.
Which one of the following set of quantum numbers is not possible for $$4p$$ electron? A
$$n = 4,l = 1,m = - 1,{m_s} = + \frac{1}{2}$$
B
$$n = 4,l = 1,m = 0,{m_s} = + \frac{1}{2}$$
C
$$n = 4,l = 1,m = 2,{m_s} = + \frac{1}{2}$$
D
$$n = 4,l = 1,m = - 1,{m_s} = - \frac{1}{2}$$
Answer :
$$n = 4,l = 1,m = 2,{m_s} = + \frac{1}{2}$$
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$${\text{For }}4p{\text{ electron}}\,n = 4,l = 1,$$ $$m = - 1,0 + 1\,{\text{and}}\,s = + \frac{1}{2}\,{\text{or}}\, - \frac{1}{2}$$
77.
Compare the energies of two radiations $${E_1}$$ with wavelength $$800\,nm$$ and $${E_2}$$ with wavelength $$400\,nm.$$ A
$${E_1} = 2{E_2}$$
B
$${E_1} = {E_2}$$
C
$${E_2} = 2{E_1}$$
D
$${E_2} = - \frac{1}{2}{E_1}$$
Answer :
$${E_2} = 2{E_1}$$
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$${E_1} = \frac{{hc}}{{{\lambda _1}}},{E_2} = \frac{{hc}}{{{\lambda _2}}}$$
78.
In a multi-electron atom, which of the following orbitals described by the three quantum members will have the same energy in the absence of magnetic and electric fields? A
(D) and (E)
B
(C) and (D)
C
(B) and (C)
D
(A) and (B)
Answer :
(D) and (E)
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The energy of an orbital is given by $$\left( {n + l} \right).$$
79.
Which of the sequences given below shows the correct increasing order of energy ? A
$$3s,3p,4s,4p,3d,5s,5p,4d$$
B
$$3s,3p,3d,4s,4p,4d,5s,5p$$
C
$$3s,3p,4s,3d,4p,5s,4d,5p$$
D
$$3s,3p,4s,4p,5s,3d,4d,5p$$
Answer :
$$3s,3p,4s,3d,4p,5s,4d,5p$$
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$$3s,3p,4s,3d,4p,5s,4d,5p$$ is the correct order of orbitals with increasing energy.
80.
Rutherford’s scattering experiment is related to the size of the A
nucleus
B
atom
C
electron
D
neutron
Answer :
nucleus
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According to Rutherford's experiment. "The central part consisting of whole of the positive charge and most of the mass, called nucleus, is extremely small in size compared to the size of the atom."