D And F Block Elements(12th Grade > Chemistry ) Questions and answers for exam Preparation

12th Grade > Chemistry

D AND F BLOCK ELEMENTS MCQs

Total Questions : 43 | Page 3 of 5 pages

Question 21. Cerium (Z = 58) is an important member of the lanthanoids. Which of the following statements about cerium is incorrect?

The +4 oxidation state of cerium is not known in solutions
The +3 oxidation state of cerium is more stable than the +4 oxidation state
The common oxidation states of cerium are +3 and +4
Cerium (IV) acts as an oxidizing agent.

Discuss Question

Answer: Option A. -> The +4 oxidation state of cerium is not known in solutions
:
A
(+4) oxidation state of cerium is also known in solution.The formation of Ce(+4) is favoured by its noble gas configuration, but it is a strong oxidant reverting to thecommon +3 state.

Question 22. The lanthanide contraction is responsible for the fact that

Zr and Y have about the same radius
Zr and Nb have similar oxidation state
Zr and Hf have about the same radius
Zr and Zn have the same oxidation sate

Discuss Question

Answer: Option C. -> Zr and Hf have about the same radius
:
C
Atomic radii down the group for transition elements first increases, becomes almost equal and then decreases. This is due to poor shielding ofone of 4felectron by another in the subshellwhich results in greater effective nuclear charge; this effect is called lanthanide contraction.

Question 23. Four successive members of the first row transition elements are listed below with their atomic numbers. Which one of them is expected to have the highest third ionization enthalpy?

Vanadium (Z = 23)
Chromium (Z = 24)
Iron (Z = 26)
Manganese (Z = 25)

Discuss Question

Answer: Option D. -> Manganese (Z = 25)
:
D

25_{M n}

3 d^{5} 4 s^{2}

After losing two electron electronic configuration will be like this

M n^{2 +} (3 d^{5})

and this is most stable configuration due to half filled orbitals hence third ionization enthalpy will be highest in this case.

Question 24. Which of the following electronic configuration is that of a transitional element?

1s2,2s2p6,3s2p6d10,4s2p6
1s2,2s2p6,3s2p6d10,4s2p1
1s2,2s2p6,3s2p6d2,4s2
1s2,2s2p6,3s2p6d6,4s2

Discuss Question

Answer: Option C. -> 1s2,2s2p6,3s2p6d2,4s2
:
C

d^{1 - 9}

configuration is transition element.

Question 25. The atomic number 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

Discuss Question

Answer: Option B. -> Cr
:
B

V =

1 s^{2}, 2 s^{2}, 2 p^{6}, 3 s^{2}, 3 p^{6}, 3 d^{3}, 4 s^{2}

Cr =

1 s^{2}, 2 s^{2}, 2 p^{6}, 3 s^{2}, 3 p^{6}, 3 d^{3}, 4 s^{1}

V =

1 s^{2}, 2 s^{2}, 2 p^{6}, 3 s^{2}, 3 p^{6}, 3 d^{5}, 4 s^{2}

Fe =

1 s^{2}, 2 s^{2}, 2 p^{6}, 3 s^{2}, 3 p^{6}, 3 d^{6}, 4 s^{2}

In second ionization enthalpy Cr

^{+}

has exact half filledd-sub shell.

Question 26. In first transition series, the melting point of Mn is low because

Due to d10 configuration, metallic bonds are strong
Due to d7 configuration, metallic bonds are weak
Due to d5 configuration, metallic bonds are weak
None of these

Discuss Question

Answer: Option C. -> Due to d5 configuration, metallic bonds are weak
:
C
Due to

d^{5}

configuration, metallic bonds are weak.

d^{5}

orbital is half filled as a result 3delectrons are more tightly held by the nucleus and this reduces the de-localization of electrons resulting in weaker metallic bonding.

Question 27. Choose incorrect option:-

KMnO4 is isostructural with KClO4
MnO2 when treated with fused KOH and oxidized in air, it gives KMnO4(purple)
Permanganate anion is diamagnetic
Both manganate and permanganate anions are tetrahedral

Discuss Question

Answer: Option B. -> MnO2 when treated with fused KOH and oxidized in air, it gives KMnO4(purple)
:
B

M n O_{2}

when treated with fused KOH and oxidized in air, it gives

K_{2} M n O_{4}

(purple)

2 M n O_{+} 4 K O H + O_{2} ⟶ 2 K_{2} M n O_{4} + 2 H_{2} O

Question 28. Which of the following is paramagnetic in nature?

Lu3+
Ce4+
Eu2+
Yb2+

Discuss Question

Answer: Option C. -> Eu2+
:
C
Lanthanoids exhibitf0

(C e^{4 +})

and thef14(Yb

^{2 +}

and Lu

^{3 +}

) configurations with no unpaired electron, thus, they are diamagnetic, whereas, Eu

^{2 +}

exhibits f7 configuration with seven unpaired electrons.

Question 29. In which of the following metallic bond is strongest?

Discuss Question

Answer: Option D. -> Cr
:
D
Strength of metallic bond depends upon number of unpaired electrons. As number of unpaired electrons increases, the bond strength increases. So Cr,Mo,Wshow stronger bonding due to maximum number of unpaired electron.

Question 30. Arrange