Chemistry (School & UG)

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Chemistry (School & UG)

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The Chemistry (School & UG) category covers the fundamental to advanced concepts of Chemistry, structured to support Class 11–12 students, competitive exam aspirants, and undergraduate learners. The content emphasizes conceptual clarity, problem-solving skills, and strong alignment with NCERT and university syllabi.

In this category, you will study:

Physical Chemistry – atomic structure, thermodynamics, chemical kinetics, equilibrium, electrochemistry, and solutions
Organic Chemistry – basic principles, reaction mechanisms, hydrocarbons, functional groups, biomolecules, and polymers
Inorganic Chemistry – periodic trends, chemical bonding, coordination compounds, metallurgy, and s-, p-, d-, and f-block elements
Numerical problem-solving – formula-based calculations, mole concept, and graph-based questions
Reaction mechanisms and derivations with step-by-step explanations
Comparisons, trends, and exceptions important for exams
NCERT-based theory, supported by diagrams, tables, MCQs, assertion–reason questions, numericals, and PYQs

The content is designed to build strong foundations, improve analytical and quantitative skills, and prepare students for school examinations, competitive exams, and undergraduate assessments.

Develop a clear, logical, and application-oriented understanding of Chemistry to excel academically and confidently tackle problem-based and conceptual questions at both school and UG levels.

Analytical Techniques Inorganic Chemistry Organic Chemistry Physical Chemistry

Q. What is Le Chatelier's principle?

A. A system at equilibrium will shift to counteract changes.
B. The rate of a reaction is proportional to the concentration of reactants.
C. Energy is conserved in chemical reactions.
D. The entropy of a system always increases.

Solution

Le Chatelier's principle states that if a system at equilibrium is subjected to a change, the system will adjust to counteract that change.

Correct Answer: A — A system at equilibrium will shift to counteract changes.

Q. What is the Beer-Lambert Law equation?

A. A = εcl
B. A = c/εl
C. A = l/εc
D. A = cl/ε

Solution

The Beer-Lambert Law is expressed as A = εcl, where A is absorbance, ε is molar absorptivity, c is concentration, and l is path length.

Correct Answer: A — A = εcl

Q. What is the Beer-Lambert Law used for in UV-Vis spectroscopy?

A. To calculate the wavelength of light
B. To determine the concentration of a solution
C. To measure the intensity of emitted light
D. To analyze the molecular structure

Solution

The Beer-Lambert Law relates the absorbance of light to the concentration of a solution, allowing for concentration determination.

Correct Answer: B — To determine the concentration of a solution

Q. What is the bond angle in a water (H2O) molecule?

A. 90 degrees
B. 104.5 degrees
C. 120 degrees
D. 180 degrees

Solution

The bond angle in water is approximately 104.5 degrees due to the repulsion of the two lone pairs.

Correct Answer: B — 104.5 degrees

Q. What is the bond angle in the H2O molecule?

A. 90 degrees
B. 104.5 degrees
C. 120 degrees
D. 180 degrees

Solution

The bond angle in H2O is approximately 104.5 degrees due to the bent shape of the molecule caused by the two lone pairs on the oxygen atom.

Correct Answer: B — 104.5 degrees

Q. What is the bond order of a molecule with 10 electrons in a molecular orbital diagram?

A. 0
B. 1
C. 2
D. 3

Solution

Bond order = (number of bonding electrons - number of antibonding electrons) / 2. For 10 electrons, if all are bonding, bond order = 10/2 = 5. If 2 are antibonding, bond order = (10-2)/2 = 4. The most stable configuration gives a bond order of 2.

Correct Answer: C — 2

Q. What is the bond order of a molecule with 10 electrons in a molecular orbital diagram showing 5 bonding and 5 antibonding electrons?

A. 0
B. 1
C. 2
D. 3

Solution

Bond order = (Number of bonding electrons - Number of antibonding electrons) / 2 = (5 - 5) / 2 = 0.

Correct Answer: A — 0

Q. What is the bond order of a molecule with 10 electrons in bonding orbitals and 4 electrons in antibonding orbitals?

A. 1
B. 2
C. 3
D. 0

Solution

Bond order = (Number of bonding electrons - Number of antibonding electrons) / 2 = (10 - 4) / 2 = 3.

Correct Answer: B — 2

Q. What is the bond order of a molecule with 3 bonding electrons and 1 antibonding electron?

A. 0.5
B. 1
C. 1.5
D. 2

Solution

Bond order = (Number of bonding electrons - Number of antibonding electrons) / 2 = (3 - 1) / 2 = 1.

Correct Answer: B — 1

Q. What is the bond order of O2 if it has 12 electrons in bonding orbitals and 4 in antibonding orbitals?

A. 2
B. 3
C. 1
D. 0

Solution

Bond order = (12 - 4) / 2 = 4. The bond order for O2 is actually 2, but this question is hypothetical.

Correct Answer: A — 2

Q. What is the bond order of the molecule N2?

A. 1
B. 2
C. 3
D. 4

Solution

N2 has 10 bonding electrons and 2 antibonding electrons, so bond order = (10 - 2) / 2 = 4 / 2 = 2.

Correct Answer: C — 3

Q. What is the bond order of the molecule O2?

A. 1
B. 2
C. 3
D. 0

Solution

O2 has 12 total valence electrons. The bond order is calculated as (number of bonding electrons - number of antibonding electrons) / 2 = (10 - 2) / 2 = 4 / 2 = 2.

Correct Answer: B — 2

Q. What is the bond order of the O2 molecule?

A. 1
B. 2
C. 3
D. 0

Solution

O2 has 12 total electrons, with 10 in bonding orbitals and 2 in antibonding orbitals. Bond order = (number of bonding electrons - number of antibonding electrons) / 2 = (10 - 2) / 2 = 4 / 2 = 2.

Correct Answer: B — 2

Q. What is the change in enthalpy (ΔH) for an endothermic reaction?

A. ΔH < 0
B. ΔH = 0
C. ΔH > 0
D. ΔH = -RT

Solution

In an endothermic reaction, heat is absorbed from the surroundings, resulting in a positive change in enthalpy (ΔH > 0).

Correct Answer: C — ΔH > 0

Q. What is the change in enthalpy (ΔH) for an exothermic reaction?

A. ΔH > 0
B. ΔH < 0
C. ΔH = 0
D. ΔH is undefined

Solution

In an exothermic reaction, heat is released, resulting in a negative change in enthalpy (ΔH < 0).

Correct Answer: B — ΔH < 0

Q. What is the change in enthalpy (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) if the bond enthalpies are: H-H = 436 kJ/mol, O=O = 498 kJ/mol, H-O = 463 kJ/mol?

A. −484 kJ
B. −572 kJ
C. −572 kJ
D. −484 kJ

Solution

ΔH = Σ(bond enthalpies of reactants) - Σ(bond enthalpies of products) = [2(436) + 498] - [4(463)] = −572 kJ.

Correct Answer: B — −572 kJ

Q. What is the change in enthalpy (ΔH) for the reaction: H2(g) + 1/2 O2(g) → H2O(l) if the standard enthalpy of formation of H2O(l) is -285.83 kJ/mol?

A. -285.83 kJ/mol
B. 285.83 kJ/mol
C. 0 kJ/mol
D. 571.66 kJ/mol

Solution

The change in enthalpy for the reaction is equal to the standard enthalpy of formation of H2O(l), which is -285.83 kJ/mol.

Correct Answer: A — -285.83 kJ/mol

Q. What is the change in enthalpy (ΔH) for the reaction: H2(g) + 1/2 O2(g) → H2O(l) if the standard enthalpy of formation of H2O(l) is -285.8 kJ/mol?

A. -285.8 kJ/mol
B. 285.8 kJ/mol
C. 0 kJ/mol
D. 571.6 kJ/mol

Solution

The change in enthalpy for the reaction is equal to the standard enthalpy of formation of H2O(l), which is -285.8 kJ/mol.

Correct Answer: A — -285.8 kJ/mol

Q. What is the change in enthalpy for the reaction at constant pressure?

A. It is equal to the heat absorbed or released.
B. It is equal to the work done on the system.
C. It is always negative.
D. It is independent of the path taken.

Solution

At constant pressure, the change in enthalpy (ΔH) is defined as the heat absorbed or released by the system.

Correct Answer: A — It is equal to the heat absorbed or released.

Q. What is the common name for 2-methylpropan-1-ol?

A. Isobutanol
B. Butanol
C. Propanol
D. Pentanol

Solution

2-methylpropan-1-ol is commonly known as isobutanol.

Correct Answer: A — Isobutanol

Q. What is the common use of alkenes in the industry?

A. Fuel
B. Plastics production
C. Solvents
D. Food additives

Solution

Alkenes are commonly used in the production of plastics, such as polyethylene.

Correct Answer: B — Plastics production

Q. What is the concentration of hydroxide ions in a solution with a pH of 11?

A. 1 x 10^-3 M
B. 1 x 10^-4 M
C. 1 x 10^-5 M
D. 1 x 10^-6 M

Solution

pOH = 14 - pH = 14 - 11 = 3. [OH-] = 10^-pOH = 10^-3 M.

Correct Answer: A — 1 x 10^-3 M

Q. What is the conjugate base of H2SO4?

A. HSO4-
B. SO4^2-
C. H3O+
D. H2O

Solution

The conjugate base of H2SO4 is HSO4-, formed when H2SO4 donates a proton (H+).

Correct Answer: A — HSO4-

Q. What is the coordination number of a metal in a complex with a tetrahedral geometry?

A. 2
B. 4
C. 6
D. 8

Solution

In a tetrahedral complex, the coordination number is 4, as there are four ligands surrounding the central metal atom.

Correct Answer: B — 4

Q. What is the coordination number of a metal in a complex with an octahedral geometry?

A. 2
B. 4
C. 6
D. 8

Solution

In an octahedral complex, the coordination number is 6, as there are six ligands surrounding the central metal atom.

Correct Answer: C — 6

Q. What is the coordination number of a metal in a complex with six ligands?

A. 2
B. 4
C. 6
D. 8

Solution

The coordination number is defined as the number of ligand atoms that are bonded to the central metal atom. In this case, with six ligands, the coordination number is 6.

Correct Answer: C — 6

Q. What is the coordination number of hydrogen in the complex ion [H2O]2+?

A. 1
B. 2
C. 3
D. 4

Solution

In the complex ion [H2O]2+, the coordination number of hydrogen is 2.

Correct Answer: B — 2

Q. What is the coordination number of hydrogen in the complex [Ni(H2)6]?

A. 2
B. 4
C. 6
D. 8

Solution

In the complex [Ni(H2)6], the coordination number of hydrogen is 6, as there are six hydrogen ligands coordinated to nickel.

Correct Answer: C — 6

Q. What is the coordination number of the central metal ion in a complex with the formula [Co(NH3)6]Cl3?

A. 2
B. 4
C. 6
D. 8

Solution

The coordination number is determined by the number of ligands attached to the central metal ion. In this case, there are six NH3 ligands, giving a coordination number of 6.

Correct Answer: C — 6

Q. What is the coordination number of the central metal ion in the complex [Cu(NH3)4]SO4?

A. 2
B. 4
C. 6
D. 8

Solution

The coordination number of copper in [Cu(NH3)4]SO4 is 4, as it is surrounded by four ammonia ligands.

Correct Answer: B — 4

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