D and F Block — NEET UG practice

82 questions

Practice NEET UG D and F Block questions free — each with a detailed solution, graded instantly. Nothing is saved; log in to track your accuracy and build a streak.

Start free practice

Sample questions with solutions

Q1 · 2026

The calculated 'spin-only' magnetic moment $\mathrm{Ti}^{2+}\left(3 \mathrm{~d}^2\right)$ is :

A.
5.92 BM
B.
3.87 BM
C.
2.84 BM
D.
4.90 BM

Answer: C

The spin-only magnetic moment of an ion depends only on the number of unpaired electrons it has. Given that magnetic moment arises from electron spin,

\mu = \sqrt{n(n+2)} \ \text{BM}

where $n$ is the number of unpaired electrons.

For $\mathrm{Ti}^{2+}$ , the electronic configuration is $[\mathrm{Ar}]3d^2 4s^0$ , since two electrons are removed from the neutral titanium atom.
In the $3d^2$ configuration, by Hund's rule the two electrons occupy two different d-orbitals with parallel spins, so there are 2 unpaired electrons.

n = 2

Substituting $n = 2$ into the formula,

\mu = \sqrt{2(2+2)} = \sqrt{8} \approx 2.84 \ \text{BM}

Hence, the spin-only magnetic moment of $\mathrm{Ti}^{2+}$ is approximately 2.84 BM. Hence, the answer is C.

Q2 · 2026

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Generally, $3 d$ transition metals have high melting points.

Reason R: Involvement of $3 d$ -electrons in addition to $4 s$ -electrons in the interatomic metallic bonding.

In light of the above statements, choose the most appropriate answer from the options given below:

A.
A is not correct but R is correct
B.
Both A and R are correct and R is the correct explanation of A
C.
Both A and R are correct and R is NOT the correct explanation of A
D.
A is correct but R is not correct.

Answer: B

The melting point of a metal depends on the strength of metallic bonding, which depends on how many electrons take part in forming the electron sea holding the metal atoms together.
In transition metals, both the outer $4s$ electrons and the inner $3d$ electrons can participate in this bonding, because the energies of $3d$ and $4s$ orbitals are close to each other.

\text{Bonding electrons} = 4s \text{ electrons} + 3d \text{ electrons}

Since more electrons are delocalised and involved in bonding, the metallic bonds become stronger, and stronger bonds require more energy (higher temperature) to break.
This directly explains why Assertion A is true, and it explains why it is true, which is exactly what Reason R states.
Since both statements are correct and R correctly explains A, this matches option B. Hence, the answer is B.

Q3 · 2026

Match List I with List II :

List I (Transition metal/compound/complex)	List II (Catalytic Role)
A. $\mathrm{V}_2\mathrm{O}_5$	I. Preparation of ammonia from $\mathrm{N}_2/\mathrm{H}_2$ mixture
B. Fe	II. Polymerisation of alkynes
C. $\mathrm{PdCl}_2$	III. Preparation of $\mathrm{H}_2\mathrm{SO}_4$ and $\mathrm{SO}_2$
D. Ni complex	IV. Oxidation of ethyne to ethanal

Choose the correct answer from the options given below.

A.
A-III, B-IV, C-I, D-II
B.
A-IV, B-I, C-III, D-II
C.
A-II, B-I, C-IV, D-III
D.
A-III, B-I, C-IV, D-II

Answer: D

To solve this matching question, recall the specific industrial or laboratory role of each catalyst mentioned in List I.
$\mathrm{V}_2\mathrm{O}_5$ is used in the Contact Process to oxidise $\mathrm{SO}_2$ to $\mathrm{SO}_3$ , a key step in manufacturing sulphuric acid.

\mathrm{A} \rightarrow \mathrm{III}

Fe (iron) is the catalyst used in the Haber process, which combines nitrogen and hydrogen gas to form ammonia.

\mathrm{B} \rightarrow \mathrm{I}

$\mathrm{PdCl}_2$ is used in the Wacker process, where it helps oxidise ethyne-type substrates to acetaldehyde (ethanal).

\mathrm{C} \rightarrow \mathrm{IV}

A Ni complex catalyst is used for the polymerisation of alkynes.

\mathrm{D} \rightarrow \mathrm{II}

Combining all four matches gives A-III, B-I, C-IV, D-II. Hence, the answer is D.

Do more with a free account

Take it as a timed mock test
Build a daily streak
Track accuracy & progress
Save questions to your library