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Chapter 8: d & f Block Elements

NCERT Solutions for CBSE Class 10 Chemistry — 12 solved questions with detailed explanations.

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Solved Questions

Q1. The element with the highest number of oxidation states in the first transition series is:

Ti
Cr
Mn
Fe

Difficulty: Easy-Medium · Topic: Transition Metals

Solution

Mn shows oxidation states from +2 to +7 (most varied). Mn has 5 unpaired d electrons + 2 s electrons.

Q2. Lanthanide contraction is due to:

Poor shielding by 4f electrons
Increase in nuclear charge only
Decrease in atomic number
Loss of d electrons

Difficulty: Easy-Medium · Topic: Lanthanides

Solution

4f electrons shield nuclear charge poorly, so effective nuclear charge increases across lanthanides, causing contraction.

Q3. Which of the following ions is colored?

Sc³⁺
Ti³⁺
Zn²⁺
Cu⁺

Difficulty: Easy-Medium · Topic: Color of Ions

Solution

Ti³⁺ has 1 unpaired d electron (d¹) and shows purple color due to d-d transitions. Sc³⁺(d⁰), Zn²⁺(d¹⁰), Cu⁺(d¹⁰) are colorless.

Q4. Transition metals show variable oxidation states because:

p electrons
f electrons
d electrons are close in energy to s electrons
s electrons only

Difficulty: Easy-Medium · Topic: d & f Block Elements

Solution

d electrons are close in energy to s electrons.

Q5. Transition metal compounds are often colored due to:

d-d electronic transitions
nuclear effects
s-p transitions
f-f transitions

Difficulty: Easy-Medium · Topic: d & f Block Elements

Solution

d-d electronic transitions.

Q6. Transition metals often form complexes because:

low charge
no d orbitals
small size and high charge density
large size

Difficulty: Easy-Medium · Topic: d & f Block Elements

Solution

small size and high charge density.

Q7. KMnO₄ is a strong:

acid
oxidizing agent
base
reducing agent

Difficulty: Easy-Medium · Topic: d & f Block Elements

Solution

oxidizing agent.

Q8. K₂Cr₂O₇ in acidic medium acts as:

oxidizing agent
base
reducing agent
catalyst

Difficulty: Easy-Medium · Topic: d & f Block Elements

Solution

oxidizing agent.

Q9. Electronic configuration of Fe²⁺ (Z=26):

[Ar]3d⁵ 4s¹
[Ar]3d⁶
[Ar]3d⁶ 4s²
[Ar]3d⁴ 4s²

Difficulty: Medium · Topic: Ion Configuration

Solution

Fe²⁺ (Z=26) has configuration [Ar]3d⁶.

Q10. Electronic configuration of Fe³⁺ (Z=26):

[Ar]3d⁴ 4s²
[Ar]3d⁶
[Ar]3d³ 4s²
[Ar]3d⁵

Difficulty: Medium · Topic: Ion Configuration

Solution

Fe³⁺ (Z=26) has configuration [Ar]3d⁵.

Q11. Electronic configuration of Cu⁺ (Z=29):

[Ar]3d¹⁰
[Ar]3d⁹ 4s¹
[Ar]3d⁸ 4s²
[Ar]3d¹⁰ 4s¹

Difficulty: Medium · Topic: Ion Configuration

Solution

Cu⁺ (Z=29) has configuration [Ar]3d¹⁰.

Q12. Electronic configuration of Cu²⁺ (Z=29):

[Ar]3d⁸ 4s¹
[Ar]3d¹⁰
[Ar]3d⁹
[Ar]3d⁷ 4s²

Difficulty: Medium · Topic: Ion Configuration

Solution

Cu²⁺ (Z=29) has configuration [Ar]3d⁹.

Other Chapters in Chemistry

Ch 1: Solid State Ch 2: Solutions Ch 3: Electrochemistry Ch 4: Chemical Kinetics Ch 5: Surface Chemistry Ch 6: Isolation of Elements Ch 7: p-Block Elements Ch 9: Coordination Compounds Ch 10: Haloalkanes & Haloarenes Ch 11: Alcohols Phenols Ethers Ch 12: Aldehydes Ketones Ch 13: Amines Ch 14: Biomolecules Ch 15: Polymers Ch 16: Chemistry in Everyday Life

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