A red solid is insoluble in water. However it becomes soluble if some KI is added to water. Heating the red solid in a testtube results in liberation of some violet coloured fumes and droplets of ametal appear on the cooler parts of the testtube. The red solid is

HgI₂
HgO
Pb₃O₄
(NH4)₂Cr₂O₇

Solution

Among the following series of transition metal ions, the one where all metal ions have 3d² electronic configuration is(At. nos. Ti =22; V= 23; Cr =24; Mn = 25)

Ti³⁺, V²⁺,Cr³⁺,Mn⁴⁺
Ti⁺, V⁴⁺,Cr⁶⁺,Mn⁷⁺
Ti⁴⁺, V³⁺,Cr²⁺,Mn³⁺
Ti²⁺, V³⁺,Cr⁴⁺,Mn⁵⁺

Solution

Which one of the following metals has a different lattice from those of the others?

Solution

Fe has hcp lattice while all other given metals have ccp lattice.

he correct order of ionic radii of Y³⁺, La³⁺, Eu³⁺ and Lu³⁺ is

(Atomic nos. Y =39, La = 57, Eu = 63, Lu = 71)

La³⁺ < Eu³⁺ < Lu³⁺ < Y³⁺
Y³⁺ < La³⁺ < Eu³⁺ < Lu³⁺
Y³⁺ < Lu³⁺ < Eu³⁺ < La³⁺
Lu³⁺ < Eu³⁺ < La³⁺ < Y³⁺

Solution

In lanthanide series there is a regular decrease in the atomic as well as ionic radii of trivalent ions (M³⁺) as the atomic number increases. Although the atomic radii do show some irregularities but ionic radii decreases from La(103 pm) to Lu (86pm). Y³⁺ belong to second transition series there fore have greater ionic radii then other ions of third transition series.

The basic character of the transition metal monoxides follows the order(Atomic Nos.,Ti = 22, V = 23, Cr = 24,Fe = 26)

TiO > VO >CrO > FeO
VO > CrO> TiO > FeO
CrO > VO > FeO > TiO
TiO > FeO > VO > CrO

Solution

The order of basic character of the transition metal monoxide is TiO > VO > CrO > FeO because basic character of oxides decreases with increase in atomic number.

Consider the following statements

(I) La(OH)₃ is the leastbasic among hydroxides of lanthanides.

(II) Zr⁴⁺ and Hf⁴⁺ posses almost the same ionic radii.

(III) Ce⁴⁺ can as an oxidizing agent.Which of the above is/are true ?

(I) and(III)
(II) and (III)
(II) only
(I) and(II)

Solution

As a result of lanthanide contraction Zr⁴⁺ and Hf⁴⁺ possess almost the same ionic radii. Ce⁴⁺ is anoxidising agent. Ce⁴⁺ gains electron to acquire morestable Ce⁴⁺ state. La(OH)₃ is the most basic among lanthanide hydroxides.

To an aqueous solution containing anions a few drops of acidified KMnO₄ are added. Which one of the following anions, if present will not decolourise the KMnO₄ solution?

I^-
\(CO_{3}^{2-}\)
S^2-
\(NO_{2}^{-}\)

Solution

Iron exhibits +2 and + 3 oxidation states. Which of the following statements about iron is incorrect ?

Ferrous oxide is more basic in nature than the ferric oxide.
Ferrous compounds are relatively more ionic than the corresponding ferric compounds.
Ferrous compounds are less volatile than the corresponding ferric compounds.
Ferrous compounds are more easily hydrolysed than the corresponding ferric compounds.

Solution

Fe³⁺ is easily hydrolysed than Fe²⁺ due to more positive charge.

The outer electron configuration of Gd (Atomic No. : 64) is :

4f³ 5d⁵ 6s²
4f⁸ 5d⁰ 6s²
4f⁴ 5d⁴6s²
4f⁷ 5d¹ 6s²

Solution

The configuration of Gd is [xe] 4f⁷ 5d¹ 6s²

In context of the lanthanoids,which of the following statements is not correct?

There is agradual decrease in the radii of the members with increasing atomic number in the series.
All the members exhibit +3 oxidation state.
Because of similar properties the separation of lanthanoids is not easy.
Availability of 4f electrons results in the formation of compounds in +4 state for all the members of the series.

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