NIOS Class 12 Chemistry Important Questions (2025): Complete Preparation Guide

NIOS Class 12 Chemistry 313 Important Questions 2026 – Chapter-Wise Objective Question Bank

Chemistry is the subject most students feel they have prepared well — and then the exam asks them to pick the correct unit for Avogadro's constant from four options that all look nearly identical. If you are preparing for NIOS Class 12 Chemistry (Code 313) in 2026 and want to know which objective questions actually matter chapter by chapter, this page breaks it all down. Sample questions with answers are included. For the complete solution booklet, contact Unnati Education at 9654279279 or 9899436384.

NIOS Chemistry 313 – Quick Subject Overview

What Are NIOS Class 12 Chemistry 313 Important Questions for 2026?

Reading Chemistry and practising Chemistry as objective questions are two entirely different things. You can read that Avogadro's constant is 6.022 × 10²³ mol⁻¹ and feel confident — until the exam puts four options in front of you where three of them use almost the same number but with different units or exponents. That is the exact point where question practice separates students who score well from those who just studied hard. NIOS Chemistry 313 spans 8 modules and 32 lessons, covering everything from chemical arithmetic and bonding to electrochemistry, organic reactions, and environmental chemistry. This page gives you the most important sample questions from the actual Unnati Education Chemistry 313 objective booklet. For the full solution set, contact Unnati Education.

Module I – Some Basic Concepts of Chemistry

Lesson 1 – Atoms, Molecules and Chemical Arithmetic

This lesson looks straightforward and that is exactly why students underestimate it. Avogadro's number, molar volume at STP, empirical formula calculation, and the laws of chemical combination are tested with specific numerical choices designed to catch students who know the concept but not the precise value.

Students who need their NIOS Class 12 TMA for Chemistry 313 solved accurately and ready for submission can get it from Unnati Education in both typed and handwritten formats.

Sample Questions

Which of the following correctly represents Avogadro's constant? A. 6.022 × 10²³ mol B. 6.022 × 10²³ mol⁻¹ C. 1.66 × 10⁻²⁴ g D. 3.011 × 10²² mol⁻¹
Answer: B

The correct empirical formula of glucose (C₆H₁₂O₆) is: A. C₆H₁₂O₆ B. CH₂O C. C₂H₄O₂ D. C₃H₆O₃
Answer: B

Fill in the Blank The volume occupied by 0.25 mol of O₂ gas at STP is __________ L.
Answer: 5.675 (since 1 mol = 22.7 L, so 0.25 × 22.7 = 5.675 L)

True or False Newton is a base SI unit.
Answer: False

The difference between options A and B in the Avogadro question is just the unit — mol versus mol⁻¹. The exam builds these traps deliberately. If you know the unit, you get the mark. If you only know the number, you might not.

Module II – Atomic Structure and Chemical Bonding

Lesson 2 – Atomic Structure

Heisenberg's Uncertainty Principle, mass number, electronic configuration, and quantum numbers are all standard exam areas from this lesson. The most common objective question format here is a "which statement is wrong" type, where one option directly contradicts a principle and the others support it.

Sample Questions

Which of the following statements contradicts Heisenberg's Uncertainty Principle? A. We can simultaneously know the exact position and momentum of an electron B. An orbital is a region where the probability of finding an electron is maximum C. Electrons exhibit wave nature D. Measurement of position affects momentum
Answer: A

The mass number of an atom is defined as: A. Number of protons B. Number of electrons C. Sum of protons and neutrons D. Sum of electrons and neutrons
Answer: C

Fill in the Blank Mass number A = Z (protons) + __________.
Answer: neutrons

Lesson 4 – Chemical Bonding

Bond angles, lattice energy, VSEPR theory, and hybridisation are the main objective areas from this lesson. Lattice energy being the most stabilising factor in an ionic compound is tested every year. The bond angle comparison between water and ammonia is another reliable question — water has a smaller bond angle (104.5°) than ammonia (107°) because water has two lone pairs on oxygen versus one on nitrogen.

Students who want comprehensive practice across all 32 lessons can get the complete NIOS Class 12 Important Questions booklet for Chemistry 313 from Unnati Education with full solutions and step-by-step working.

Sample Questions

Which step in the Born-Haber cycle contributes the most to stabilising an ionic compound? A. Ionisation energy B. Electron affinity C. Sublimation energy D. Lattice energy
Answer: D

The bond angle in water is less than in ammonia because: A. Oxygen is more electronegative than nitrogen B. Lone pair–lone pair repulsion is maximum in water C. Water has hydrogen bonding D. Water has higher bond enthalpy
Answer: B

Fill in the Blank The geometry of a water molecule according to VSEPR theory is __________.
Answer: bent (V-shaped)

Module III – States of Matter

Lesson 7 – Solutions

Solutions is where numerical objective questions are most concentrated in Module III. Molality being temperature-independent (because it is based on mass, not volume) is one of the most tested facts in the entire Chemistry 313 paper. The dissociation calculation for electrolytes — where Na₂SO₄ gives 3 ions — is also a standard numerical MCQ.

Sample Questions

Which of the following concentration units is temperature-independent? A. Molarity B. Normality C. Molality D. Mass by volume percentage
Answer: C

A 0.1 M Na₂SO₄ solution contributes how many effective particles in solution? A. 0.1 mol B. 0.2 mol C. 0.3 mol D. 0.4 mol
Answer: C (Na₂SO₄ → 2Na⁺ + SO₄²⁻ → 3 ions × 0.1 = 0.3 mol)

True or False Boiling point elevation depends only on the number of solute particles, not their nature.
Answer: True

Module IV – Chemical Energetics

Lesson 9 – Chemical Thermodynamics

System classification and property types are the main objective areas here. A closed system exchanges energy but not matter. An isolated system exchanges neither. These definitions are tested in identification MCQs where the exam gives you a scenario and asks you to name the system type.

Sample Questions

Which of the following systems is an example of a closed system? A. Water in an open pan B. Hot tea in a thermos with stopper C. A plant exchanging gases D. A sealed steel container with water
Answer: D

Which of the following is an extensive property? A. Temperature B. Density C. Mass D. Refractive index
Answer: C

Fill in the Blank A system that can exchange neither energy nor matter with its surroundings is called an __________ system.
Answer: isolated

True or False An exothermic reaction has a negative value of ΔH.
Answer: True

Module V – Chemical Dynamics

Lesson 12 – Ionic Equilibrium

Ionic equilibrium is tested for conjugate acid-base pairs (the pair must differ by exactly one proton), degree of ionisation behaviour, and buffer solutions. The Bronsted-Lowry concept is the framework the exam uses here. HCl and Cl⁻ are a conjugate pair because removing one proton from HCl gives Cl⁻.

Students who want to study from actual past NIOS papers can get NIOS Class 12 question paper collections for Chemistry 313 from Unnati Education, covering multiple exam cycles with complete solutions.

Sample Questions

Which of the following combinations represents a conjugate acid-base pair? A. NH₄⁺ / OH⁻ B. HCl / Cl⁻ C. H₂O / H₃O⁺ D. CH₃COOH / NH₄⁺
Answer: B

The degree of ionisation (α) of a weak acid increases with: A. Increasing concentration of acid B. Presence of common ion C. Increasing temperature D. Addition of a strong acid
Answer: C

Fill in the Blank A solution that resists change in pH upon the addition of small amounts of acid or base is called a __________ solution.
Answer: buffer

Lesson 13 – Electrochemistry

Electrochemistry has two specific values the exam tests in almost every paper. Fluorine has the highest standard reduction potential at +2.87 V, making it the strongest oxidising agent. Zinc has E° = −0.76 V, making it a good reducing agent. These numbers appear as direct identification MCQs — know both and you have those marks.

Students who need NIOS Class 12 Intext and Terminal Questions for Chemistry 313 can get the complete chapter-wise set from Unnati Education for preparation across all lessons.

Sample Questions

Which element in the electrochemical series has the highest oxidising power? A. Fluorine B. Chlorine C. Manganese D. Oxygen
Answer: A (E° = +2.87 V)

What is the standard electrode potential (E°) for the Zn²⁺/Zn electrode? A. +0.76 V B. −0.44 V C. −0.76 V D. +0.34 V
Answer: C

True or False A higher standard reduction potential indicates a greater tendency to get reduced.
Answer: True

Module VI – Chemistry of Elements

Lesson 17 – Hydrogen and s-Block Elements

Three facts from this lesson appear in objective questions consistently — tritium is radioactive, hydrogen forms H⁻ (like halide ions), and the half-life of tritium is approximately 12.3 years. These are direct identification questions that take five seconds once you know the fact.

Sample Questions

Which isotope of hydrogen is radioactive in nature? A. Protium B. Deuterium C. Tritium D. None of these
Answer: C

Hydrogen shows resemblance with halogens because: A. It forms H⁻ like halide ions B. It has one proton C. It is highly electronegative D. It forms H⁺ ion only
Answer: A

Fill in the Blank The half-life of tritium is approximately __________ years.
Answer: 12.3

Lesson 21 – d-Block and f-Block Elements

Transition element questions are very precise. Zinc is not a transition element because its 3d orbital is completely filled in both atomic and ionic states — no partially filled d-orbitals. Chromium's abnormal configuration arises from exchange energy favouring half-filled orbitals. Both facts are tested year after year.

Sample Questions

Which of the following elements does not qualify as a transition element according to the IUPAC definition? A. Fe B. Zn C. Cu D. Cr
Answer: B

The abnormal electronic configuration of chromium is due to: A. Exchange energy and stability of half-filled orbitals B. High ionisation enthalpy C. Low electronegativity D. Lanthanide contraction
Answer: A

Fill in the Blank Zinc is not a transition element because its 3d orbital is completely __________ in both atomic and common ionic states.
Answer: filled

Lesson 22 – Coordination Compounds

Coordination compound questions test how many ions a given complex produces in solution, what a chelating ligand is, and IUPAC nomenclature rules. These are very direct factual questions once you know Werner's theory clearly.

Sample Questions

In [Co(NH₃)₅Cl]Cl₂, how many ions are produced in solution? A. 1 B. 2 C. 3 D. 0
Answer: C

Which of the following is a chelating ligand? A. NH₃ B. H₂O C. Ethylenediamine (en) D. CN⁻
Answer: C

Fill in the Blank A ligand that donates two electron pairs to a central metal ion is called a __________ ligand.
Answer: bidentate

Module VII – Organic Chemistry

Lesson 24 – Hydrocarbons and Lesson 25 – Haloalkanes

Kolbe's electrolysis always forms alkanes with an even number of carbon atoms — this fact appears as a direct MCQ practically every year. In haloalkanes, para-isomers have higher melting points than ortho- or meta-isomers because of their greater symmetry and tighter crystal packing. IUPAC naming using the lowest locant rule is tested with structures given directly.

Sample Questions

Which method gives a higher alkane with an even number of carbon atoms? A. Wurtz Reaction B. Kolbe's Electrolysis C. Catalytic hydrogenation D. Reduction of carboxylic acids
Answer: B

Which of the following haloarenes has the highest melting point? A. o-Dichlorobenzene B. m-Dichlorobenzene C. p-Dichlorobenzene D. Chlorobenzene
Answer: C

Fill in the Blank The IUPAC name of CH₃–CH(Cl)–CH(CH₃)–CH₂CH₃ is __________.
Answer: 2-Chloro-3-methylpentane

True or False Para-isomers have higher melting points than ortho-isomers due to greater molecular symmetry.
Answer: True

Lesson 27 – Aldehydes, Ketones and Carboxylic Acids

The iodoform test and nucleophilic addition reactivity are the two most tested areas from this lesson. Ethanal gives iodoform because it has the CH₃CO– group. Formaldehyde is the most reactive toward nucleophilic addition because it has no alkyl groups causing steric hindrance or electron donation.

Sample Questions

Which of the following compounds gives a positive iodoform test? A. Formaldehyde B. Ethanal C. Benzaldehyde D. Methanoic acid
Answer: B

Which compound is most reactive toward nucleophilic addition? A. Propanone B. Butanone C. Benzaldehyde D. Formaldehyde
Answer: D

Fill in the Blank The iodoform test gives a yellow precipitate of __________ with methyl ketones.
Answer: CHI₃

True or False Ketones undergo the Cannizzaro reaction.
Answer: False

Lesson 29 – Biomolecules

Biomolecule questions are factual and direct. The correct definition of carbohydrates, the distinction between α- and β-anomers at C-1, and the secondary structure of proteins are all tested in MCQ and fill-in-the-blank format.

Sample Questions

Which of the following correctly defines carbohydrates? A. Compounds made of carbon and hydrogen only B. Polyhydroxy aldehydes or ketones or their hydrolysis products C. Organic compounds without functional groups D. Simple esters of sugars
Answer: B

Which of the following pairs represent α- and β-anomers of glucose? A. D-glucose and L-glucose B. Open chain and cyclic form of glucose C. Two cyclic forms differing at the C-1 hydroxyl group D. Glucose and galactose
Answer: C

Fill in the Blank The secondary structure of a protein refers to the __________ or beta-sheet arrangement maintained by hydrogen bonds.
Answer: alpha-helix

Module VIII – Chemistry in Everyday Life

Acid rain from SO₂ and NO₂, analgesic drug classification, and biodegradable versus non-biodegradable detergents are the standard objective areas from Module VIII. Students who prepare these lessons pick up marks that others give away simply by not reading the last module.

Sample Questions

The pollutant primarily responsible for acid rain is: A. CO₂ and CH₄ B. SO₂ and NO₂ C. O₃ and N₂ D. CO and H₂O
Answer: B

Fill in the Blank Biodegradable detergents have __________ hydrocarbon chains that can be broken down by bacteria.
Answer: straight (unbranched)

True or False Ozone in the stratosphere protects the Earth from harmful ultraviolet radiation.
Answer: True

Key Reference Table – Most Tested Facts by Module

Common Mistakes Students Make in Chemistry 313 Exam

Writing Avogadro's constant with the unit mol instead of mol⁻¹ — the exam puts both as options and students pick the wrong one because they memorised the number but not the unit. Confusing molality with molarity when asked which is temperature-independent costs straightforward marks every year. Saying the bond angle in water is larger than in ammonia when it is actually smaller is a VSEPR error that appears in true or false questions. Thinking zinc is a transition element because it sits in the d-block — it is not, and the IUPAC definition is clear about partially filled d-orbitals. Confusing ethanal with formaldehyde in the iodoform test question because both are aldehydes but only one has the CH₃CO– group. Not preparing Module VIII at all because it seems less important, and then losing five to six marks from direct one-line questions that took thirty seconds to learn.

About Unnati Education

Unnati Education has been supporting NIOS students since 2010 and our Chemistry 313 booklet is built around one core idea — what the exam actually tests, not what textbooks explain at length. We provide a complete chapter-wise objective question booklet covering all 32 lessons across all 8 modules with correct answers and clear working. We also offer solved TMAs, previous year question papers with complete solutions, and chapter-wise notes — all updated for both the April and October 2026 NIOS exam cycles.

How to Get the Complete Solutions

If you want the full NIOS Class 12 Chemistry 313 important questions booklet with complete solutions for 2026, or if you need previous year question papers, solved TMAs, or module-wise notes, contact Unnati Education today.

Phone and WhatsApp: 9654279279 or 9899436384 Website: unnatieducations.com/nios

Frequently Asked Questions

Q1. Are these NIOS Class 12 Chemistry 313 important questions enough for the 2026 exam?

These chapter-wise questions cover the most important objective topics from all 8 modules and 32 lessons of NIOS Chemistry 313. They are a focused and reliable preparation resource for 2026. For the complete solution booklet with answers and full working for every chapter, contact Unnati Education at 9654279279 or 9899436384 and get your copy without any delay.

Q2. Where can I get or download the NIOS Chemistry 313 important questions PDF for 2026?

Unnati Education provides a complete NIOS Chemistry 313 important questions PDF with MCQs, fill in the blanks, and true or false questions from all chapters, with full answers and step-by-step solutions included. Call or WhatsApp at 9654279279 or 9899436384 and our team will share the complete material with you quickly and directly without any waiting.

Q3. Does the booklet cover organic chemistry and everyday chemistry from Chemistry 313?

Yes, the Unnati Education booklet for NIOS Chemistry 313 covers objective questions from all 8 modules including the full organic chemistry section from Module VII and chemistry in everyday life from Module VIII. Every question has a correct answer with clear explanation. Contact us at 9654279279 or 9899436384 to get your complete 2026 booklet today.

Q4. Can I get previous year question papers for NIOS Chemistry 313 from Unnati Education?

Yes, Unnati Education provides previous year question papers with complete solutions for NIOS Chemistry 313. These papers show how questions are framed, which chapters carry more weight, and what specific facts the exam targets across all modules. Call or WhatsApp at 9654279279 or 9899436384 to get the full paper set for the 2026 exam cycle.

Q5. Is the Unnati Education booklet valid for both April and October 2026 NIOS Chemistry exams?

Yes, the Unnati Education objective question booklet for NIOS Chemistry 313 is fully valid for both the April and October 2026 NIOS exam cycles. All content is based on the current NIOS syllabus and is reviewed throughout the year. Whichever exam cycle you are appearing in, this booklet prepares you completely for the objective section of your Chemistry paper.

The subject can seem difficult, but if you have the right materials and a good strategy, it will be a rewarding one. Unnati Education's NIOS Class 12 Chemistry Important Questions are designed with care to help students prepare and succeed.

To achieve maximum results, begin practicing as early as possible, focus more on understanding than memorization, and use our Chemistry 313 important questions to help you.

Prepare intelligently. Study in a systematic way. Score well.