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 4 of 5 pages

Question 31. The electronic configuration of Ag atom is

[Kr]3d105s1
[Xe]4f14d106s1
[Kr]4d105s1
[Kr]4d95s2

Discuss Question

Answer: Option C. -> [Kr]4d105s1
:
C
[Kr]

4 d^{10} 5 s^{1}

(atomic no. = 47)

Question 32. Which of the following element has maximum first ionisation potential

Discuss Question

Answer: Option D. -> Mn
:
D
The first ionization energies of Ti,V,Cr and Mnare 656, 650, 652 and 717kJ/molerespectively. I.E. increase in a period fromL

\to

R hence, manganese has maximum first ionisation potential.

Question 33. Amongst

T i F_{6}^{2 -}, C o F_{6}^{3 -}, C u_{2} C l_{2}

and

N i C l_{4}^{2 -}

(Atomic number Ti=22,Co=27,Cu=29,Ni=28 The colourless species are

CoF3−6 and NiCl2−4
TiF2−6 and CoF3−6
Cu2Cl2 and NiCl2−4
TiF2−6 and Cu2Cl2

Discuss Question

Answer: Option D. -> TiF2−6 and Cu2Cl2
:
D

T i F_{6}^{2 -}

and

C u_{2} C l_{2}

due to absence of unpaired electrons.

Question 34. Ferric iodide is very unstable but ferric chloride is a stable compound. This is because

hydration energy of ferric iodide is less than that of ferric chloride
I− ion is a stronger reducing agent as compared to Cl− ion and thus, Fe3+ is easily reduced by I− ion to Fe2+ ion.
ferric iodide is a covalent compound whereas ferric chloride is ionic
ferric iodide is a covalent compound whereas ferric chloride is ionic

Discuss Question

Answer: Option B. -> I− ion is a stronger reducing agent as compared to Cl− ion and thus, Fe3+ is easily reduced by I− ion to Fe2+ ion.
:
B

2 F e^{3 +} + 2 I^{-} ⟶ 2 F e^{2 +} + I_{2}

Question 35. In chromite ore, the oxidation number of iron and chromium are respectively

+3, +2
+3, +2
+2, +6
+2, +3.

Discuss Question

Answer: Option D. -> +2, +3.
:
D
Chromite ore is

F e C r_{2} O_{4}

F e O . C r_{2} O_{3}

. Oxidation state of Fe = +2, Cr= +3.

Question 36. Which of the following statement is wrong about intersititial compounds?

they are very hard
they retain metallic conductivity
their melting points are lower than those of pure metals
they are chemically inert.

Discuss Question

Answer: Option C. -> their melting points are lower than those of pure metals
:
C
Melting point of interstitial compounds are higher than those of pure metals.

Question 37. Which of the following compounds has color but not unpaired electrons?

MnO2
KMnO4
K2MnO4
MnCl2

Discuss Question

Answer: Option B. -> KMnO4
:
B

K M n O_{4}

is purple color but Mn is in +7 oxidation state (

d^{0}

configuration). The color is not due to d-d transition but it is due to charge transfer transition from ligand (oxygen) to metal (manganese).

Question 38. Choose correct option:-
1. Zinc forms colored ions
2.

[C o F_{6}]^{3 -}

is paramagnetic
3.Sc forms +4 oxidation state
4. Zinc is not a transition element

1 and 2
1 and 3
2 and 4
3 and 4

Discuss Question

Answer: Option C. -> 2 and 4
:
C
Option 1-

Z n^{2 +}

has no unpaired electrons, it is diamagnetic and thus, colorless.
Option 2- In co-ordination compound

[C o F_{6}]^{3 -}

C o^{3 +}

has 4 unpaired electrons, thus, it is paramagnetic.
Option 3- Maximum oxidation state shown by Sc is +3.
Option 4- Zinc atom has completely filled d orbitals

(3 d^{10})

in its ground state as well as in its oxidised state, hence it is not regarded as a transition element.

Question 39. In aqueous solution, Eu

^{2} +

ion acts as a/an

oxidizing agent
reducing agent
either a) or b)
none of these.

Discuss Question

Answer: Option B. -> reducing agent
:
B
Eu

^{2} +

has strong tendency to be oxidized to more stable Eu

^{3} +

. Therefore, it acts as a reducing agent.

Question 40. The element showing most stable +8 oxidation state in its compound is

Discuss Question

Answer: Option A. -> Os
:
A
Both Ru and Os show +8 oxidation state in their compounds but +8 oxidation state shown by Os is more stable as compared to that of Ru.