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 Which of the following ions does not liberate hydrogen gas on reaction with dilute acids ?
Option: 1 Ti2+
Option: 2 V2+
Option: 3  Cr2+
Option: 4  Mn2+  
 

The reactivity of transition metals decreases from Ti?????2+ to V??????2+ Ito Cr?????2+ and finally Mn2+. Therefore, the reactivity of Mn2+ is very less. Therefore, Mn?????2+ does not liberate hydrogen gas on reaction with dilute acids. 

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Posted by

vishal kumar

The atomic radius of Ag is closest to:
Option: 1 Au
Option: 2 Ni
Option: 3 Hg
Option: 4 Cu
 

Atomic Size/Radii -

Because of the lanthanide contraction, the size of the elements of the 4d series is similar to their corresponding elements of 5d series.

Thus, the atomic radius of Ag is closest to Au.

Therefore, Option(1) is correct.

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Posted by

Kuldeep Maurya

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Consider the following reactions: NaCl+K_{2}Cr_{2}O_{7}+H_{2}SO_{4} (conc.)\rightarrow A + side\ products A+NaOH\rightarrow B + side\ products B+ H_{2}SO_{4} (dil.)+H_{2}O_{2}\rightarrow C+ side\ products The sum of the total number of atoms in one molecule each of A, B and C is:  
Option: 1 18
Option: 216
Option: 3 14
Option: 4 20
 

(A) = CrO2Cl2

(B) = Na2CrO4

(C) = CrO5 

Total atoms = 5 (A) + 7 (B) + 6 (C) = 18 atoms

Thus, the correct answer is 18.

Therefore, option(1) is correct

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Posted by

Kuldeep Maurya

The lanthanide does not show +4 oxidation state is:
 
Option: 1 Tb 
Option: 2 Tb 
Option: 3 Tb 
Option: 4 Tb 
Option: 5 Ce
Option: 6 Ce
Option: 7 Ce
Option: 8 Ce
Option: 9 Eu  
Option: 10 Eu  
Option: 11 Eu  
Option: 12 Eu  
Option: 13 Dy
Option: 14 Dy
Option: 15 Dy
Option: 16 Dy

Eu does not show +4 oxidation state.

Therefore, Option(3) is correct.

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Posted by

Kuldeep Maurya

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The incorrect statement is:
 
Option: 1 Brass is an alloy of copper and nickel.
Option: 2 Dust iron is used to manufacture brought iron.
Option: 3 German silver is an alloy of zinc, copper and nickel.
Option: 4Bronze is an alloy of copper and tin
 

Brass is an alloy of copper and zinc, but not of copper and nickel. Thus, other statements are correct.

Therefore, Option(1) is correct.

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Posted by

Kuldeep Maurya

Mischmetal is an alloy consisting mainly of :
Option: 1 lanthanoid metals
Option: 2 actionoid and transition metals
Option: 3 Lanthanoid and actionoid metals
Option: 4 actionoid metals

Mischmetal is an alloy of lanthanoid metals with Fe.

It consists of a lanthanoid metal (~95%) and iron (~5%) and traces of S, C, Ca, and Al.

Therefore, the correct option is (1).

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Posted by

Kuldeep Maurya

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The correct electronic configuration and spin-only magnetic moment (BM) of \mathrm{Gd}^{3+}(\mathrm{Z}=64), respectively, are :
Option: 1 \text { [Xe] } 4 \mathrm{f}^{7} \text { and } 8.9
Option: 2 \text { [Xe] } 4 \mathrm{f}^{7} \text { and } 7.9
Option: 3 \text { [Xe] } 5 \mathrm{f}^{7} \text { and } 8.9
Option: 4 \text { [Xe] } 5 \mathrm{f}^{7} \text { and } 7.9

Electronic configuration of \mathrm{Gd}^{3+} \text { is }{ }_{64} \mathrm{Gd}^{3+}=[\mathrm{Xe}] 4 \mathrm{f}^{7} 

Gd3+ has 7 unpaired electrons and the magnetic moment is given as 

Magnetic moment  ({\mu})=\sqrt{\mathrm{n}(\mathrm{n}+2)} \mathrm{B.} \mathrm{M.}

Where n = number of unpaired electrons.

So, 

\mu=\sqrt{7(7+2) } = 7.9\ \mathrm{B.} \mathrm{M.}

Therefore, the correct option is (2).

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Posted by

Kuldeep Maurya

The incorrect statement(s) among (a)-(c) is (are): (a) W(VI) is more stable than Cr(VI) (b) in the presence of HCl, permaganate titrations provide satisfactory results. (c) some lanthnoid oxides can be used as phosphorous
Option: 1 (b) and (c) only
Option: 2 (a) and (b) only
Option: 3 (b) only
Option: 4 (a) only

(a) W(VI) is more stable than Cr(VI). It is true and given in NCERT.

(b) in the presence of HCl permanganate titrations provide satisfactory results. It is incorrect.

Permanganate titrations in presence of hydrochloric acid are unsatisfactory since hydrochloric acid is oxidised to chlorine.

(c) Some individual Ln oxides are used as phosphors in television screens and similar fluorescing surfaces.

So,(b) is incorrect.

Therefore, the correct option is (3).

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Kuldeep Maurya

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The oxidation states of transition metal atoms in K_{2}Cr_{2}O_{7} , KMnO_{4} and K_{2}FeO_{4} , respectively are X, Y and Z , the sum of X, Y and Z is ___________
 

In K2Cr2O7, Cr is in +6, thus, x = 6

In KMnO4, Mn is in +7, thus, y = 7

In K2FeO4, Fe is in +6, thus, z = 6

Thus, we have:

x + y + z = 6 + 7 + 6 = 19

Therefore, the correct answer is 19.

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Posted by

Kuldeep Maurya

The oxide that shows magnetic property is:
Option: 1 Mn3O4
Option: 2 SiO2
Option: 3 Na2O
Option: 4 MgO

\mathrm{Mn_3O_4} exists as \mathrm{MnO.Mn_2O_3} and is paramagnetic

The oxidation state of \mathrm{Mn} in \mathrm{Mn_3O_4} is +2 and +3.

Both \mathrm{Mn^{2+}} and \mathrm{Mn^{3+}} contain unpaired electrons and are paramagnetic

\mathrm{M n^{2+}-[A r] 3 d^{5} 4 s^{0}}

\mathrm{M n^{3+}-[A r] 3 d^{4} 4 s^{0}}

All other oxides are diamagnetic due to absence of unpaired electrons.

Therefore, the Correct option is (1)

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Posted by

Kuldeep Maurya

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