Practice Start Test

d and f Block Elements

JEE Chemistry · 278 questions · Page 5 of 28 · Click an option or "Show Solution" to reveal answer

Q41
The atomic numbers of vanadium (V), Chromium (Cr), manganese (Mn) and iron (Fe) are respectively 23, 24, 25 and 26. Which one of these may be expected to have the highest second ionization enthalpy?
A Cr
B Mn
C Fe
D V
Correct Answer
Option A
Solution

Due to stable electronic configuration of Cr+1 ion (3d5)

Q42
Larger number of oxidation states are exhibited by the actinoids than those by the lanthanoids, the main reason being :
A 4f orbitals more diffused than the 5f orbitals
B lesser energy difference between 5f and 6d than between 4f and 5d orbitals
C more energy difference between 5f and 6d than between 4f and 5d orbitals
D more reactive nature of the actinoids than the lanthanoids
Correct Answer
Option B
Solution

NOTE : The main reason for exhibiting larger number of oxidation states by actinoids as compared to lanthanoids is lesser energy difference between

5f5f

and

6d6d

orbitals as compared to that between

4f4f

and

5d5d

orbitals.

Q43
In context with the transition elements, which of the following statements is incorrect ?
A In addition to the normal oxidation states, the zero oxidation state is also shown by these elements in complexes.
B In the highest oxidation states, the transition metal show basic character and form cationic complexes.
C In the highest oxidation states of the first five transition elements (Sc to Mn), all the 4s and 3d electrons are used for bonding
D Once the d5 configuration is exceeded, the tendency to involve all the 3d electrons in bonding decreases.
Correct Answer
Option B
Solution

Lower oxidation state of an element forms more basic oxide and hydroxide, while the higher oxidation state will form more acidic oxide/hydroxide.

For example,

Q44
Knowing that the Chemistry of lanthanoids (Ln) is dominated by its +3 oxidation state, which of the following statements is incorrect?
A Because of the large size of the Ln (III) ions the bonding in its compounds is predominantly ionic in character.
B The ionic sizes of Ln (III) decrease in general with increasing atomic number.
C Ln (III) compounds are generally colourless
D Ln (III) hydroxides are mainly basic in character.
Correct Answer
Option C
Solution

Most of the

Ln3+  L{n^{3 + }}\,\,

compounds except

La3+L{a^{3 + }}

and

Lu3+L{u^{3 + }}

are coloured due to the presence of

ff

-electrons.

Q45
In context of the lanthanoids, which of the following statements is not correct?
A All the members exhibit +3 oxidation state
B Because of similar properties the separation of lanthanoids is not easy.
C Availability of 4f electrons results in the formation of compounds in +4 state for all the members of the series.
D There is a gradual decrease in the radii of the members with increasing atomic number in the series.
Correct Answer
Option C
Solution

The number stable oxidation states of lanthanides is

+3+3

.

Q46
In the given chemical reaction, colors of the Fe2+ and Fe3+ ions, are respectively : 5Fe2+ + MnO4−_4^ - + 8H+ →\to Mn2+ + 4H2O + 5Fe3+
A Yellow, Orange
B Yellow, Green
C Green, Orange
D Green, Yellow
Correct Answer
Option D
Solution

Colour of Fe2+ is observed green and Fe3+ is yellow.

Q47
The colour of KMnO4 is due to :
A d – d transition
B L →\to M charge transfer transition
C σ\sigma – σ\sigma* transition
D M →\to L charge transfer transition
Correct Answer
Option B
Solution
L→ML \to M

charge transfer spectra.

KMnO4KMn{O_4}

is colored because it absorbs light in the visible range of electromagnetic radiation.

The permanganate ion is the source of color, as a ligand to metal,

(L→M)\left( {L \to M} \right)

charge transfer takes place between oxygen's

pp

orbitals and the empty

dd

-orbitals on the metal.

This charge transfer takes place when a photon of light is absorbed, which leads to the purple color of the compound.

Q48
The transition metal ions responsible for color in ruby and emerald are, respectively :
A Cr3+ and Co3+
B Co3+ and Cr3+
C Co3+ and Co3+
D Cr3+ and Cr3+
Correct Answer
Option D
Solution

On addition of impurities to the colourless gemstones, brilliant colours are produced.

On addition of chromium to colourless corundum (Al2O3), a red ruby is formed.

Red colour ruby is obtained when Cr3+ ions replace Al3+ ions in the octahedral sites of corundum.

A green emerald emerges when chromium is added to colourless beryl (Be3Al2(SiO3)6).

Green colour emerald is obtained when Cr3+ ions replace Al3+ in the octahedral site of beryl.

Q49
Which of the following compounds is metallic and ferromagnetic ?
A CrO2
B VO2
C MnO2
D TiO2
Correct Answer
Option A
Solution

Out of all the four given metallic oxides

CrO2Cr{O_2}

is attracted by magnetic field very strongly. The effect persists even when the magnetic field is removed. Thus

CrO2Cr{O_2}

is metallic and ferromagnetic in nature.

Q50
The incorrect statement is :
A Cu2+ salts give red coloured borax bead test in reducing flame.
B Cu2+ and Ni2+ ions give black precipitate with H2S in presence of HCl solution.
C Ferric ion gives blood red color with potasium thiocyanate.
D Cu2+ ion gives chocolate coloured preciitate with potassium ferrocyanide solution.
Correct Answer
Option B
Solution

Cu2+ and Ni2+ ions belong to Group II and Group IV respectively.

Group II sulphides precipitated out even under low concentration of sulphides, while Group IV sulphides require higher concentration of sulphides.

To fulfill this reaction condition, dil.

HCl is chosen in Group II reagents and NH4OH is chosen in Group IV reagents.

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