WBSCTE Diploma 1st Semester Applied Chemistry MCQ with Answer & Explanation

Applied Chemistry MCQ Practice Set 1 (Atomic Structure)

Preparing for the WBSCTE Diploma 1st Semester Applied Chemistry examination? This post contains important Applied Chemistry MCQs with correct answers and simple explanations to help Diploma Engineering students prepare effectively for their semester examination.

Instead of simply memorizing answers, understanding the basic concepts behind each question is important for performing well in Applied Chemistry. This MCQ practice set is designed to help students improve their conceptual understanding, accuracy, and confidence.

This post is especially useful for Diploma Engineering 1st Semester students preparing for their semester examination.

Q. Which of the following quantum numbers governs the spatial orientation of an atomic orbital? [2021]

• (a) Principal quantum number
• (b) Azimuthal quantum number
• (c) Magnetic quantum number
• (d) Spin quantum number

Correct Answer: (c) Magnetic quantum number

Explanation: The magnetic quantum number (m​) specifies the orientation of an orbital in space. The principal quantum number ($n$) determines the shell and energy level, while the azimuthal quantum number ($l$) determines the subshell and orbital shape.

Q. According to Bohr’s theory, the orbits in which electrons move are: [2021]

• (a) Elliptical
• (b) Cylindrical
• (c) Circular
• (d) Oval

Correct Answer: (c) Circular

Explanation: According to Bohr’s atomic model, electrons revolve around the nucleus in fixed circular orbits of definite energy, called stationary orbits. Electrons do not radiate energy while remaining in these permitted orbits.

Q. How many atomic orbitals are present in the fourth energy level ($n=4$) of an atom? [2022]

• (a) 32
• (b) 16
• (c) 8
• (d) 4

Correct Answer: (b) 16

Explanation: The total number of orbitals in a shell is given by n2. For $n=4$, the number of orbitals is $=16$, consisting of 1 s, 3 p, 5 d, and 7 f orbitals.

Q. Rutherford’s experiment on scattering of $\alpha$-particles showed for the first time that the atom has: [2022]

• (a) Electrons
• (b) Protons
• (c) Nucleus
• (d) Neutrons

Correct Answer: (c) Nucleus

Explanation: Rutherford’s $\alpha$-particle scattering experiment established that an atom contains a small, dense, positively charged nucleus that contains most of the atom’s mass. It also showed that most of the atom is empty space.

Q. Number of electrons present in the $d$ orbital of Fe3+ ion is: [2023]

• (a) 4
• (b) 5
• (c) 6
• (d) 7

Correct Answer: (b) 5

Explanation: Iron ($Fe$, $Z=26$) has the configuration [Ar]3d64s2. On forming Fe3+, two $4s$ electrons and one $3d$ electron are removed, giving [Ar]3d5. Therefore, Fe3+ has 5 electrons in its $d$ subshell.

Q. The maximum number of electrons that can be accommodated in a $d$ sub-shell is: [2024]

• (a) 5
• (b) 10
• (c) 20
• (d) 2

Correct Answer: (b) 10

Explanation: A $d$ subshell contains 5 orbitals, and each orbital can accommodate a maximum of 2 electrons according to the Pauli exclusion principle. Therefore, maximum electrons = $5\times 2=10$

Q. Number of sub-shells present in the M-shell ($n=3$) is: [2025]

• (a) 2
• (b) 3
• (c) 4
• (d) 5

Correct Answer: (b) 3

Explanation: For $n=3$, the azimuthal quantum number $l$ can have values 0, 1, and 2, corresponding to the $3s$, $3p$, and $3d$ subshells. Hence, the M-shell contains 3 subshells.

Q. In the ground state, an element has 13 electrons in its M-shell. The element is: [2025]

• (a) Chromium
• (b) Iron
• (c) Nickel
• (d) Copper

Correct Answer: (a) Chromium

Explanation: Chromium ($Z=24$) has the ground-state configuration [Ar]3d54s1. The M-shell ($n=3$) contains 3s2+3p6+3d5=13 electrons. Therefore, the element is Chromium.