Some Basic Concepts of ChemistryNEET MCQs with solutions

Not quite — the answer is A.

The mole (mol) is the SI base unit for amount of substance. Kilogram is for mass, candela for luminous intensity, and ampere for electric current — all SI base units but for different physical quantities.

Not quite — the answer is B.

Moles = given mass / molar mass = 46 / 23 = 2 mol. This is a direct mole-mass conversion using n = m/M.

Not quite — the answer is A.

Coefficients directly give mole ratio: H₂:O₂ = 2:1. Option B (1:2) is the classic inversion trap — students reverse numerator and denominator. Option C (1:1) results from ignoring coefficients entirely.

Not quite — the answer is B.

Law of definite proportions (Proust) states that a compound always contains elements in the same fixed mass ratio regardless of source or method of preparation. Law of multiple proportions applies when two elements form more than one compound.

Not quite — the answer is A.

Mass percent expresses solute mass as a fraction of total solution mass, making it independent of temperature. Option B is wrong — dividing by volume gives w/v percent, not w/w.

Not quite — the answer is A.

18 g H2O has molar mass 18 g mol−1, so it contains 1 mol of molecules. 44 g CO2 has molar mass 44 g mol−1, so it also contains 1 mol of molecules. Equal moles contain equal numbers of molecules by Avogadro's law, so the ratio is 1:1. Options 1:2, 2:1 and 9:22 are incorrect because the mole counts are equal.

Not quite — the answer is C.

18 g H2O = 18/18 = 1 mol of molecules. Each H2O molecule contains 3 atoms (2 H + 1 O). Total atoms = 1 × 3 × 6.022 × 10²³ = 1.8066 × 10²⁴. Option A is simply Nₐ (1 mol atoms). Option B is 2Nₐ, counting only hydrogen atoms. Option D is 0.5Nₐ.

Not quite — the answer is A.

Chemistry is defined as the science dealing with matter — its composition, properties, and the transformations it undergoes. It is not limited to labs, organisms, or celestial bodies.

Not quite — the answer is A.

Atomic mass is expressed in atomic mass unit (u); notably, u and Dalton (Da) are the same unit — both equal 1/12th mass of C-12 atom. The distinction makes A the primary NCERT term while B is technically a synonym, not a separate answer.

Not quite — the answer is A.

Dalton proposed atoms are the smallest indivisible particles of matter that participate in chemical reactions. Options B and C directly contradict the postulate that atoms are neither created nor destroyed. Option D contradicts indivisibility — atoms do not split during compound formation.

Not quite — the answer is A.

NCERT defines matter as anything that has mass and occupies space. Visibility is irrelevant — air is matter but invisible. Matter need not react chemically or be solid.

Not quite — the answer is A.

The limiting reagent is fully consumed before other reactants, stopping the reaction. Option B is wrong — excess reagent is present in larger amount, not the limiting reagent.

Not quite — the answer is B.

The ratio C:H = 2:6 simplifies to 1:3, giving empirical formula CH₃. Option A (C₂H₆) is the molecular formula itself — the most common error. Option C (C₂H₃) traps students who reduce only the hydrogen count.

Not quite — the answer is B.

% O = (16/18) × 100 = 88.9%; hydrogen contributes only 2/18 = 11.1%, making Option A the classic swap trap. Option C (50%) falsely assumes equal mass sharing between two atoms.

Not quite — the answer is B.

NCERT explicitly states chemistry is the central science because it connects physical sciences (physics) with life sciences (biology) and applied sciences (earth science, materials). Option A is too narrow.

Not quite — the answer is C.

Vaccines involve chemical synthesis of antigens and adjuvants — a direct application of chemistry. Bridge design is engineering; planetary orbits are physics; ocean mapping is geography.

Not quite — the answer is B.

Fertilizers (urea, DAP), pesticides, and herbicides are all chemical substances manufactured through industrial chemistry. Without synthetic fertilizers, modern agricultural yield would be impossible.

Not quite — the answer is D.

Environmental science uses chemical analysis for pollution monitoring, water treatment, and remediation of toxic substances. Geology uses some chemistry but its primary tools are physical. Astronomy and nuclear physics are distinct domains.

Not quite — the answer is C.

Predicting planetary motion is governed by gravitational physics (Newton's laws, Kepler's laws) — not chemistry. Drug synthesis, polymers, and fertilizers are all direct outputs of chemical science.

Not quite — the answer is A.

Most industrial processes — from steel production to polymer synthesis — involve chemical reactions where matter undergoes compositional change. Limiting chemistry to labs is the classic misconception NEET tests.

Not quite — the answer is B.

Pure mathematics is a formal/logical discipline with no dependence on chemical principles. Medicine, agriculture, and materials science all fundamentally rely on chemistry for their core processes.

Not quite — the answer is C.

Combustion (fuel burning), electrochemical cells (batteries, fuel cells), and even nuclear chemistry involve chemical transformations. Claiming energy production is purely physics ignores electrochemistry entirely.

Not quite — the answer is D.

Digestion involves enzymatic hydrolysis — a chemical reaction breaking down macromolecules into absorbable units. Dissolving sugar is a physical change (no new substance formed). Reading and switching a fan involve no chemical change.

Not quite — the answer is A.

Chemistry is the foundation of drug synthesis, formulation, and diagnostic reagents — all core to healthcare. The other sectors do not depend on chemistry for their primary activities.