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Some Basic Concepts of Chemistry — NEET Chemistry MCQs with Solutions
Free NEET Chemistry Some Basic Concepts of Chemistry MCQs with step-by-step solutions covering Development & Importance of Chemistry, Nature of Matter, Properties of Matter & Measurement, Uncertainty in Measurement, Laws of Chemical Combination, Dalton's Atomic Theory. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Development & Importance of Chemistry · easy · theory
In ancient India, the science of chemistry was known by which of the following names?
A. Shilpa Shastra
B. Jyotish Shastra
C. Vaastu Shastra
D. Rasayan Shastra ✓ Correct
Solution: In ancient India chemistry was called Rasayan Shastra (also Rastantra, Ras Kriya or Rasvidya). It included metallurgy, medicine, and the manufacture of cosmetics, glass and dyes. The other "Shastras" listed deal with astronomy/architecture, not chemistry.
Q2 — Development & Importance of Chemistry · easy · theory
The drug AZT (Azidothymidine) is used in helping patients suffering from:
A. malaria
B. cancer
C. AIDS ✓ Correct
D. tuberculosis
Solution: The chapter states that the drug AZT (Azidothymidine) is used for helping AIDS patients. Cancer therapy uses cisplatin and taxol, so AZT is specific to AIDS, not cancer or the other diseases.
Q3 — Development & Importance of Chemistry · easy · theory
Which of the following are examples of 'Green House' gases whose management is a concern for chemists?
A. Oxygen and nitrogen
B. Hydrogen and chlorine
C. Helium and argon
D. Methane and carbon dioxide ✓ Correct
Solution: The chapter cites methane (CH₄) and carbon dioxide (CO₂) as greenhouse gases. Oxygen, nitrogen and the noble gases helium and argon are not greenhouse gases in this context.
Q4 — Nature of Matter · easy · theory
Which one of the following states of matter has a definite volume but does NOT have a definite shape?
A. Liquid ✓ Correct
B. Solid
C. Both solid and gas
D. Gas
Solution: Liquids have a definite volume but no definite shape — they take the shape of the container in which they are placed. Solids have both a definite volume and a definite shape, while gases have neither a definite volume nor a definite shape.
Q5 — Nature of Matter · easy · theory
In which state of matter are the constituent particles held very close to one another in an orderly arrangement with very little freedom of movement?
A. Gas
B. Vapour
C. Solid ✓ Correct
D. Liquid
Solution: In solids the particles are held very close together in an orderly fashion and have almost no freedom of movement, which is why solids possess a definite shape and volume. In liquids the particles are close but can move around; in gases they are far apart and move easily and fast.
Q6 — Nature of Matter · easy · theory
Which of the following is a homogeneous mixture?
A. Sand mixed with water
B. Grains mixed with small stones
C. Sugar completely dissolved in water ✓ Correct
D. A mixture of common salt and sugar
Solution: In sugar dissolved in water the sugar particles are uniformly distributed and the composition is the same throughout, so it is a homogeneous mixture. Sand–water, salt–sugar and grains–stones are heterogeneous, since their composition is not uniform and the components can be distinguished.
Q7 — Nature of Matter · easy · numerical
Water boils and changes from the liquid state to the gaseous state at 100 °C. Using K = °C + 273.15, this boiling temperature on the kelvin scale is:
A. 212 K
B. 373.15 K ✓ Correct
C. 273.15 K
D. 173.15 K
Solution: K = °C + 273.15 = 100 + 273.15 = 373.15 K. Subtracting instead of adding gives the wrong 173.15 K; 273.15 K corresponds to 0 °C (the freezing point); 212 is the Fahrenheit boiling point, not a kelvin value.
Q8 — Properties of Matter & Measurement · easy · theory
Which one of the following is a PHYSICAL property of a substance?
A. Reactivity with acids
B. Combustibility
C. Acidity
D. Density ✓ Correct
Solution: Physical properties such as colour, odour, melting point, boiling point and density can be measured or observed without changing the identity or composition of the substance. Combustibility, reactivity with acids and acidity all require a chemical change to be observed, so they are chemical properties.
Q9 — Properties of Matter & Measurement · easy · theory
Which of the following statements about mass and weight is correct?
A. The weight of a substance is constant, but its mass varies with gravity
B. The mass of a substance is constant, but its weight may vary from one place to another ✓ Correct
C. Mass and weight are the same physical quantity measured in different units
D. Mass is the force exerted by gravity on an object
Solution: Mass is the amount of matter present in a substance and stays constant everywhere. Weight is the force exerted by gravity on the object, so it can change from place to place as gravity changes. Hence only the first statement is correct.
Q10 — Properties of Matter & Measurement · easy · numerical
A block of metal has a mass of 60 g and occupies a volume of 20 cm³. Using density = mass ÷ volume, its density is:
A. 0.33 g cm⁻³
B. 3 g cm⁻³ ✓ Correct
C. 1200 g cm⁻³
D. 30 g cm⁻³
Solution: Density = mass ÷ volume = 60 g ÷ 20 cm³ = 3 g cm⁻³. Inverting the ratio (20 ÷ 60) gives the wrong 0.33 g cm⁻³, while multiplying (60 × 20) gives 1200 g cm⁻³.
Q11 — Properties of Matter & Measurement · easy · numerical
The volume of a liquid is 2.5 L. Using 1 L = 1000 cm³, this volume expressed in cm³ is:
A. 2500 cm³ ✓ Correct
B. 250 cm³
C. 25 cm³
D. 25000 cm³
Solution: Since 1 L = 1000 cm³, 2.5 L = 2.5 × 1000 = 2500 cm³. Using a factor of 100 gives 250, and a factor of 10000 gives 25000 — both are wrong powers of ten.
Q12 — Properties of Matter & Measurement · easy · numerical
A liquid has a density of 0.8 g cm⁻³. Using mass = density × volume, the mass of 50 cm³ of this liquid is:
A. 40 g ✓ Correct
B. 0.016 g
C. 62.5 g
D. 400 g
Solution: mass = density × volume = 0.8 g cm⁻³ × 50 cm³ = 40 g. Dividing volume by density (50 ÷ 0.8) gives the wrong 62.5 g.
Q13 — Uncertainty in Measurement · easy · theory
Which statement correctly distinguishes precision from accuracy?
A. Precision is the closeness of a set of repeated measurements to one another, while accuracy is the closeness of a measurement to the true value ✓ Correct
B. Precision is the closeness of a measurement to the true value, while accuracy is the closeness of repeated measurements to one another
C. Precision depends only on the observer, while accuracy depends only on the instrument
D. Precision and accuracy mean exactly the same thing
Solution: Precision refers to how close repeated measurements of the same quantity are to one another (their reproducibility), whereas accuracy refers to how close a measured value is to the true value. For example, readings 1.95 g and 1.93 g are precise (close to each other) but not accurate if the true value is 2.00 g.
Q14 — Uncertainty in Measurement · easy · numerical
How many significant figures are there in the measurement 0.00340 g?
A. 2
B. 5
C. 6
D. 3 ✓ Correct
Solution: Rule: zeros before the first non-zero digit are not significant, but zeros to the right of the decimal after a non-zero digit are significant. In 0.00340 the leading 0.00 is not counted; the digits 3, 4 and the trailing 0 are significant, giving 3 significant figures.
Q15 — Uncertainty in Measurement · easy · numerical
Express the number 0.00048 in scientific notation (N × 10ⁿ).
A. 4.8 × 10⁻³
B. 4.8 × 10⁻⁵
C. 4.8 × 10⁻⁴ ✓ Correct
D. 4.8 × 10⁴
Solution: To write 0.00048 as N × 10ⁿ with N between 1 and 10, count how many places the decimal point moves right to reach 4.8 — that is 4 places. Each right shift makes the exponent negative, so 0.00048 = 4.8 × 10⁻⁴. Miscounting the shift gives 4.8 × 10⁻³ or 4.8 × 10⁻⁵.
Q16 — Laws of Chemical Combination · easy · theory
Which law states that a given compound always contains exactly the same proportion of elements by weight, irrespective of the source of the compound?
A. Avogadro’s law
B. Law of conservation of mass
C. Law of multiple proportions
D. Law of definite proportions ✓ Correct
Solution: The law of definite (or constant) proportions was given by Joseph Proust. Working with natural and synthetic cupric carbonate he found the composition was identical (51.35% Cu, 9.74% C, 38.91% O in both), showing a pure compound always contains the same elements combined in the same proportion by mass.
Q17 — Laws of Chemical Combination · easy · theory
Avogadro’s law states that equal volumes of all gases, measured under the same conditions of temperature and pressure, contain equal numbers of:
A. electrons
B. atoms
C. protons
D. molecules ✓ Correct
Solution: Avogadro proposed in 1811 that equal volumes of all gases at the same temperature and pressure contain equal numbers of MOLECULES (not atoms). This distinction between atoms and molecules explained why 2 volumes of hydrogen react with 1 volume of oxygen to give 2 volumes of water vapour.
Q18 — Laws of Chemical Combination · easy · numerical
When 12 g of carbon is burnt completely in 32 g of oxygen, the whole of it is converted into carbon dioxide. By the law of conservation of mass, the mass of carbon dioxide formed is:
A. 20 g
B. 384 g
C. 44 g ✓ Correct
D. 22 g
Solution: C + O₂ → CO₂. Mass of products = mass of reactants = 12 g + 32 g = 44 g of CO₂. Subtracting the masses (32 − 12) wrongly gives 20 g; multiplying them (12 × 32) gives 384 g.
Q19 — Dalton's Atomic Theory · easy · theory
In which year did John Dalton publish "A New System of Chemical Philosophy", in which he put forward his atomic theory?
A. 1808 ✓ Correct
B. 1803
C. 1789
D. 1811
Solution: John Dalton published "A New System of Chemical Philosophy" in 1808. The year 1803 is when he proposed the law of multiple proportions, 1789 is when Lavoisier stated the law of conservation of mass, and 1811 is when Avogadro proposed his law.
Q20 — Dalton's Atomic Theory · easy · theory
According to Dalton’s atomic theory, which statement about the atoms of a given element is correct?
A. All atoms of a given element are identical in mass and in all other properties ✓ Correct
B. Atoms of a given element can be broken down into smaller particles
C. Atoms of a given element differ from one another in mass
D. Atoms of a given element are identical to atoms of every other element
Solution: Dalton’s second postulate states that all atoms of a given element have identical properties, including identical mass, while atoms of different elements differ in mass. The other options describe ideas that came later — isotopes and subatomic particles — which Dalton’s original theory did not include.
Q21 — Dalton's Atomic Theory · easy · theory
According to Dalton, what happens to atoms during a chemical reaction?
A. Atoms of one element are converted into atoms of another element
B. New atoms are created from energy
C. Atoms of the reactants are destroyed
D. They are only rearranged; they are neither created nor destroyed ✓ Correct
Solution: Dalton’s fourth postulate states that a chemical reaction involves only the reorganisation (rearrangement) of atoms; atoms are neither created nor destroyed. This directly accounts for the law of conservation of mass.
Q22 — Dalton's Atomic Theory · easy · theory
The term "atom" comes from the Greek word "a-tomio". What does this word mean?
A. Invisible
B. Weightless
C. Indivisible ✓ Correct
D. Spherical
Solution: "A-tomio" means indivisible. The idea of matter being made of small indivisible particles dates back to the Greek philosopher Democritus (460–370 BC); Dalton later revived it on an experimental footing. Dalton’s assumption that atoms are indivisible was itself disproved later by the discovery of subatomic particles.
Q23 — Atomic & Molecular Masses · easy · theory
On the modern carbon-12 scale, one unified atomic mass unit (1 u) is defined as a mass exactly equal to:
A. the mass of one atom of carbon-12
B. the mass of one atom of hydrogen
C. one-twelfth of the mass of one atom of oxygen-16
D. one-twelfth of the mass of one atom of carbon-12 ✓ Correct
Solution: Since 1961 the atomic mass scale takes carbon-12 as the standard, assigning ¹²C a mass of exactly 12 u. One unified atomic mass unit (1 u, formerly amu) is therefore defined as exactly one-twelfth of the mass of one ¹²C atom, which equals 1.66056 × 10⁻²⁴ g. Hydrogen and oxygen-16 are not the reference on this scale.
Q24 — Atomic & Molecular Masses · easy · numerical
Using the atomic masses H = 1 u and O = 16 u, the molecular mass of water (H₂O) is:
A. 34 u
B. 16 u
C. 18 u ✓ Correct
D. 17 u
Solution: Molecular mass = sum of atomic masses = 2 × (mass of H) + 1 × (mass of O) = 2(1) + 16 = 18 u. Using only one hydrogen atom (1 + 16) wrongly gives 17 u; doubling the whole molecule gives 34 u; counting oxygen alone gives 16 u.
Q25 — Atomic & Molecular Masses · easy · numerical
The molecular mass of carbon dioxide (CO₂), taking C = 12 u and O = 16 u, is:
A. 60 u
B. 44 u ✓ Correct
C. 28 u
D. 22 u
Solution: CO₂ has one carbon and two oxygen atoms: molecular mass = 12 + 2 × 16 = 12 + 32 = 44 u. Counting only one oxygen (12 + 16) gives 28 u (that is CO); halving gives 22 u; using three oxygen atoms (12 + 48) gives 60 u.
Q26 — Atomic & Molecular Masses · easy · numerical
Sodium chloride does not exist as discrete molecules, so we use its formula mass. With Na = 23 u and Cl = 35.5 u, the formula mass of NaCl is:
A. 58.5 u ✓ Correct
B. 46 u
C. 58 u
D. 35.5 u
Solution: Formula mass of NaCl = atomic mass of sodium + atomic mass of chlorine = 23 + 35.5 = 58.5 u. Rounding chlorine to 35 gives 58 u; counting only chlorine gives 35.5 u; taking two sodium atoms (2 × 23) gives 46 u.
Q27 — Atomic & Molecular Masses · easy · numerical
The molecular mass of ammonia (NH₃), taking N = 14 u and H = 1 u, is:
A. 14 u
B. 17 u ✓ Correct
C. 16 u
D. 15 u
Solution: NH₃ has one nitrogen and three hydrogen atoms: 14 + (3 × 1) = 14 + 3 = 17 u. Counting only one hydrogen gives 15 u; counting two hydrogens gives 16 u; counting nitrogen alone gives 14 u.
Q28 — Mole Concept & Molar Masses · easy · theory
One mole of any substance contains the same number of elementary entities. According to the modern SI definition, this number — the Avogadro number Nₐ — is:
A. 3.011 × 10²³
B. 6.022 × 10²³ ✓ Correct
C. 1.008 × 10²³
D. 6.022 × 10²⁴
Solution: The mole is the SI unit of amount of substance; one mole contains exactly 6.02214076 × 10²³ elementary entities, usually written 6.022 × 10²³. This fixed value is the Avogadro constant Nₐ (in mol⁻¹). 6.022 × 10²⁴ is ten times too large, and 3.011 × 10²³ is only half of Nₐ.
Q29 — Mole Concept & Molar Masses · easy · numerical
The number of moles present in 36 g of water (H₂O, molar mass = 18 g mol⁻¹) is:
A. 4 mol
B. 1 mol
C. 0.5 mol
D. 2 mol ✓ Correct
Solution: Number of moles n = mass ÷ molar mass = 36 g ÷ 18 g mol⁻¹ = 2 mol. Inverting the ratio (18 ÷ 36) gives 0.5 mol; assuming mass equals molar mass gives 1 mol.
Q30 — Mole Concept & Molar Masses · easy · numerical
How many molecules are present in 2 mol of carbon dioxide (CO₂)? (Nₐ = 6.022 × 10²³)
A. 3.011 × 10²³
B. 6.022 × 10²³
C. 1.2044 × 10²³
D. 1.2044 × 10²⁴ ✓ Correct
Solution: Number of molecules = moles × Nₐ = 2 × 6.022 × 10²³ = 12.044 × 10²³ = 1.2044 × 10²⁴. Forgetting to multiply by the 2 mol leaves just 6.022 × 10²³; a power-of-ten slip gives 1.2044 × 10²³.