NEET

Which of the following arrangements does not represent the correct order of the property stated against it ?

V²⁺ < Cr²⁺ < Mn²⁺ < Fe²⁺: paramagnetic behaviour
Ni²⁺ < Co²⁺ < Fe²⁺ < Mn²⁺: ionic size
Co³⁺< Fe³⁺ < Cr³⁺ < Sc³⁺: stability in aqueous solution
Sc < Ti< Cr < Mn : number of oxidation states

Solution

Oxidation states of the metal in the minerals haematite and magnetite, respectively, are

II, III in haematite and III in magnetite
II, III in haematite and II in magnetite
II, III in haematite and II in magnetite
III in haematite and II, III in magnetite

Solution

(i) Haematite is Fe₂O₃ in which Fe is present in III oxidation state.

(ii) Magnetite (Fe₃O₄) is an equimolar mixture of FeO and Fe₂O₃.Oxidation state of Fe in FeO is II.Oxidation state of Fe in Fe₂O₃ is III.

Which of the following ions will exhibit colour in aqueous solutions?

La³⁺(Z = 57)
Ti³⁺(Z = 22)
Lu³⁺(Z = 71)
Sc³⁺(Z = 21)

Solution

La³⁺: 54 e^-= [Xe]

Ti³⁺: 19 e^- = [Ar] 3d¹(Coloured)

Lu³⁺: 68 e^- = [Xe] 4f¹⁴

Sc³⁺: 18 e^- = [Ar]

Out of \(TiF_{6}^{2-}\),\(CoF_{6}^{3-}\),\(Cu_{2}Cl_{2}\) and \(NiCl_{4}^{2-}\) (Z of Ti = 22,Co =27, Cu = 29, Ni = 28), the colourless species are:

\(Cu_{2}Cl_{2}\, and\, NiCl_{4}^{2-}\)
\(TiF_{6}^{2-}\, and\, Cu_{2}Cl_{2}\)
\(CoF_{6}^{3-}\, and\, NiCl_{4}^{2-}\)
\(TiF_{6}^{2-}\, and\, CoF_{6}^{3-}\)

Solution

Lithopone is a mixture of :

ZnCO₃, BaCO₃
ZnS,Na₂SO₄
ZnSO₄, BaSO₄
ZnS, BaSO₄

Solution

Lithopone is a mixture of ZnS + BaSO₄ which is a white paint.

Which of the following statement is incorrect ?

Across a period from Sc to Cu the densities in crease with increasing atomic number.
The melting point of transition elements rise to a maximum from Sc to Cr and then decreases from Fe to Zn.
Transition elements have high enthalpies of atomization and in 3d series increase regularly from Sc to Cu.
On going down a group from 3d to 6d series the stability of higher oxidation state increases with in creasing atomic number.

Solution

(a), (b) and (d) are correct statements.(c) There is drop in enthalpy of atomization at manganese because of half filled stable electronic configuration leading to less mobilisation of electrons.This results in weaker metallic bonds.

Which one is most acidic?

Cr₂O₃
V₂O₆
Mn₂O₇
Fe₂O₃

Solution

As the oxidation state of metal associated with oxygen in creases, the acidic character of oxide increases. So Mn₂O₇ is most acidic as it has highest +7, oxidation state.

KI and CuSO₄ solutions on mixing produce :

Cu₂I₂ + K₂SO₄
Cu₂I₂+ I₂+ K₂SO₄
CuI₂+ K₂SO₄
CuI₂+ I₂+ K₂SO₄

Solution

Silver nitrate produces a black stain on skin due to

being a strong reducing agent
its corrosive action
formation of complex compound
its reduction to metallic silver

Solution

Its reduction to metallic silver.

\(2AgNO_{3}\rightarrow \underset{black stain}{2\, Ag}+N_{2}+3O_{2}\)

Philosopher’s wool is :

ZnCl₂
ZnS
Zn(NO₃)₂
ZnO

Solution

Philosopher’s wool is ZnO

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