chemistry MCQs

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chemistry MCQs

Practice complete Chemistry MCQs covering Matter, States of Matter, Physical and Chemical Changes, Atomic Structure, Chemical Bonding, Periodic Table, Acids, Bases and Salts, Metals and Non-Metals, Chemical Reactions, Electrochemistry, Organic Chemistry, Hydrocarbons, Environmental Chemistry, Polymers, Biomolecules, Nuclear Chemistry, and all other important topics. Includes chapter-wise and exam-oriented multiple-choice questions with detailed answers and explanations for JKSSB, SSC, Banking, Railway, UPSC, CUET, NEET, State PSCs, and other competitive exams.

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Question #861
Which of the following reactions is a neutralization reaction?
A. Fe + CuSO₄ → FeSO₄ + Cu
B. CaCO₃ → CaO + CO₂
C. 2Na + Cl₂ → 2NaCl
D. HCl + NaOH → NaCl + H₂O
Discuss
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Correct Answer: Option D

Explanation:
Neutralization is the reaction of an acid and a base to form salt and water. HCl (acid) + NaOH (base) → NaCl (salt) + H₂O. Option A is combination; C is decomposition; D is displacement.
This question belongs to: Science chemistry
Question #862
The pH of a sample of rain water is found to be 5.6. It is:
A. Acid rain
B. Basic
C. Acidic due to dissolved CO₂
D. Neutral
Discuss
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Correct Answer: Option C

Explanation:
Pure rainwater naturally has pH about 5.6 because CO₂ from air dissolves and forms carbonic acid. This is not considered acid rain. Acid rain has pH below 5.0 (due to SO₂ and NOₓ).
This question belongs to: Science chemistry
Question #863
Washing soda is:
A. CaOCl₂
B. NaHCO₃
C. Na₂CO₃·10H₂O
D. NaOH
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Correct Answer: Option C

Explanation:
Washing soda is sodium carbonate decahydrate (Na₂CO₃·10H₂O). Baking soda is NaHCO₃. Caustic soda is NaOH. Bleaching powder is CaOCl₂.
This question belongs to: Science chemistry
Question #864
Which metal oxide is amphoteric?
A. Al₂O₃
B. MgO
C. Na₂O
D. CuO
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Correct Answer: Option A

Explanation:
Aluminium oxide (Al₂O₃) reacts with both acids and bases, so it is amphoteric. Na₂O and MgO are basic; CuO is basic. ZnO is also amphoteric.
This question belongs to: Science chemistry
Question #865
The alloy bronze contains copper and:
A. Zinc
B. Aluminium
C. Lead
D. Tin
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Correct Answer: Option D

Explanation:
Bronze is Cu + Sn. Brass is Cu + Zn. Solder is Pb + Sn. Duralumin is Al + Cu + Mg. Bronze was one of the earliest alloys used by humans.
This question belongs to: Science chemistry
Question #866
Which allotrope of carbon is used as a neutron moderator in nuclear reactors?
A. Graphite
B. Fullerene
C. Charcoal
D. Diamond
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Correct Answer: Option A

Explanation:
Graphite slows down fast neutrons in nuclear reactors, enabling sustained chain reaction. Diamond is hard and insulating; fullerenes are nanomaterials; charcoal is adsorbent.
This question belongs to: Science chemistry
Question #867
During the electrolysis of acidified water, the volume ratio of hydrogen to oxygen collected is:
A. 1:2
B. 3:1
C. 1:1
D. 2:1
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Correct Answer: Option D

Explanation:
Water decomposes as 2H₂O → 2H₂ + O₂. So 2 volumes of H₂ for every 1 volume of O₂, ratio 2:1. Hydrogen collected at cathode, oxygen at anode.
This question belongs to: Science chemistry
Question #868
Charles' law is valid when:
A. Volume and pressure are constant
B. Only volume is constant
C. Pressure and number of moles are constant
D. Temperature and pressure are constant
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Correct Answer: Option C

Explanation:
Charles' law: V ∝ T at constant pressure and for a fixed mass (n constant). If pressure or amount changes, the relationship does not hold. The temperature must be in Kelvin.
This question belongs to: Science chemistry
Question #869
A catalyst lowers the activation energy of a reaction. This results in:
A. Increase in the equilibrium constant
B. Change in the stoichiometry
C. Increase in the rate of reaction
D. Change in enthalpy
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Correct Answer: Option C

Explanation:
Lower activation energy means more molecules have energy to cross the barrier, increasing the reaction rate. Enthalpy (ΔH) and equilibrium constant remain unchanged. Catalyst does not affect stoichiometry.
This question belongs to: Science chemistry
Question #870
Which of the following is a potassic fertilizer?
A. DAP
B. Muriate of potash
C. Urea
D. Superphosphate
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Correct Answer: Option B

Explanation:
Muriate of potash (MOP) is KCl, providing potassium. Urea is nitrogenous; DAP provides N and P; superphosphate provides phosphorus. Potassic fertilizers improve plant disease resistance.
This question belongs to: Science chemistry
Question #871
Sodium hydroxide is manufactured by:
A. Chlor-alkali process
B. Solvay process
C. Contact process
D. Haber process
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Correct Answer: Option A

Explanation:
Chlor-alkali process: electrolysis of concentrated NaCl solution (brine) yields NaOH, Cl₂, and H₂. Solvay process makes Na₂CO₃; Haber for NH₃; Contact for H₂SO₄.
This question belongs to: Science chemistry
Question #872
Ethanol can be converted to ethanoic acid by:
A. Hydrogenation
B. Fermentation
C. Dehydration
D. Oxidation
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Correct Answer: Option D

Explanation:
Oxidation of ethanol with acidified K₂Cr₂O₇ or KMnO₄ produces ethanoic acid (CH₃COOH). Dehydration gives ethene; hydrogenation adds H₂; fermentation produces ethanol from sugars.
This question belongs to: Science chemistry
Question #873
Which of the following polymers is a thermosetting plastic?
A. Bakelite
B. PVC
C. Polyethylene
D. Nylon
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Correct Answer: Option A

Explanation:
Bakelite (phenol-formaldehyde) is thermosetting; once set, it cannot be remolded. Polyethylene, PVC, and nylon are thermoplastics – they soften on heating.
This question belongs to: Science chemistry
Question #874
Hard water can be softened by ion exchange method. The resin exchanges ________ for Ca²⁺ and Mg²⁺ ions.
A. H⁺
B. OH⁻
C. Na⁺
D. Cl⁻
Discuss
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Correct Answer: Option C

Explanation:
Cation exchange resins contain Na⁺ ions which are replaced by Ca²⁺/Mg²⁺, softening the water. Anion exchange can also be used for deionization. Washing soda precipitates Ca/Mg.
This question belongs to: Science chemistry
Question #875
Ozone layer depletion is maximum over:
A. Tropic of Cancer
B. Equator
C. Antarctica
D. North Pole only
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Correct Answer: Option C

Explanation:
The 'ozone hole' is most prominent over Antarctica during spring due to unique polar stratospheric clouds and CFC accumulation. Arctic ozone depletion also occurs but is less severe.
This question belongs to: Science chemistry
Question #876
Gamma rays are produced from:
A. Friction
B. Nuclear de-excitation
C. Outer electron transitions
D. Chemical reactions
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Correct Answer: Option B

Explanation:
Gamma rays are high-energy photons emitted from the nucleus when it transitions from excited state to lower energy state. Alpha/beta decay often leaves nucleus in excited state which emits gamma.
This question belongs to: Science chemistry
Question #877
The father of modern chemistry is:
A. J.J. Thomson
B. Dmitri Mendeleev
C. John Dalton
D. Antoine Lavoisier
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Correct Answer: Option D

Explanation:
Lavoisier is known for the law of conservation of mass, naming oxygen/hydrogen, and establishing chemistry as a quantitative science. Dalton proposed atomic theory; Mendeleev periodic table.
This question belongs to: Science chemistry
Question #878
Which of the following substances sublimes on heating?
A. Sodium chloride
B. Copper
C. Sugar
D. Iodine
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Correct Answer: Option D

Explanation:
Iodine directly converts from solid to violet vapor on gentle heating (sublimation). NaCl melts; sugar decomposes; copper melts at high temperature. Other sublimable substances: camphor, naphthalene, dry ice.
This question belongs to: Science chemistry
Question #879
Isotope ¹⁴C is used for:
A. Cancer treatment
B. Smoke detectors
C. Sterilization
D. Radiocarbon dating
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Correct Answer: Option D

Explanation:
Carbon-14 (half-life ~5730 years) is used to determine the age of archaeological and geological organic samples up to ~50,000 years. Cobalt-60 for cancer; Am-241 for smoke detectors.
This question belongs to: Science chemistry
Question #880
Which of the following is a molecule of an element?
A. NaCl
B. H₂O
C. O₃
D. CO₂
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Correct Answer: Option C

Explanation:
Ozone (O₃) is a molecule consisting of three oxygen atoms, all of the same element. H₂O and CO₂ are compounds; NaCl is an ionic compound (not a discrete molecule). O₂ is also a molecule of an element.
This question belongs to: Science chemistry

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