Chemistry MCQs

Question #961

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The property of carbon to form bonds with itself is called:

A. Tetravalency

B. Isomerism

C. Catenation

D. Polymerisation

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Correct Answer: Option C

Explanation:
Catenation is the ability of carbon atoms to form long chains, rings, and networks via covalent bonds. This leads to a vast number of organic compounds. Silicon also catenates but to lesser extent.

This question belongs to: Science chemistry

Question #962

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The main component of CNG is:

A. Ethane

B. Methane

C. Propane

D. Butane

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Correct Answer: Option B

Explanation:
CNG (Compressed Natural Gas) is primarily methane (CH₄). LPG is propane and butane. Methane is the simplest hydrocarbon.

This question belongs to: Science chemistry

Question #963

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In a lead-acid battery, the electrolyte is:

A. HCl

B. HNO₃

C. Dilute H₂SO₄

D. KOH

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Correct Answer: Option C

Explanation:
Lead-acid batteries use dilute sulfuric acid (approx 35%). During discharge, H₂SO₄ concentration decreases, forming PbSO₄ on both electrodes.

This question belongs to: Science chemistry

Question #964

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The rate of effusion of two gases A and B are equal. Which is true?

A. Molar mass of A = Molar mass of B

B. Temperature must be different

C. They are the same gas

D. Pressure must be different

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Correct Answer: Option A

Explanation:
Graham's law: r ∝ 1/√M. If rA = rB, then MA = MB (at same T,P). Different gases can have same molar mass (e.g., N₂ and CO both 28).

This question belongs to: Science chemistry

Question #965

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Which catalyst is used in the decomposition of H₂O₂ in laboratory preparation of oxygen?

A. MnO₂

B. V₂O₅

C. Pt

D. Fe

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Correct Answer: Option A

Explanation:
Manganese dioxide (MnO₂) catalyzes H₂O₂ decomposition: 2H₂O₂ → 2H₂O + O₂. Finely divided MnO₂ is added. Other catalysts include catalase enzyme.

This question belongs to: Science chemistry

Question #966

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Enzymes are specific in action because:

A. They are biocatalysts

B. They are proteins

C. Their active site has a specific shape fitting the substrate

D. They are sensitive to pH

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Correct Answer: Option C

Explanation:
The 'lock-and-key' model explains enzyme specificity: the substrate fits into the active site like a key in a lock. Protein nature is general; specificity arises from 3D structure.

This question belongs to: Science chemistry

Question #967

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The impurity silica from iron ore is removed by adding:

A. Clay

B. Coke

C. Sand

D. Limestone

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Correct Answer: Option D

Explanation:
Limestone decomposes to CaO, which reacts with acidic SiO₂ to form slag CaSiO₃. Coke reduces iron oxide; sand is silica.

This question belongs to: Science chemistry

Question #968

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Which of the following is not a nitrogenous fertilizer?

A. Ammonium nitrate

B. Calcium ammonium nitrate

C. Urea

D. Superphosphate

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Correct Answer: Option D

Explanation:
Superphosphate is a phosphatic fertilizer (Ca(H₂PO₄)₂·CaSO₄). Urea, ammonium nitrate, CAN are nitrogenous.

This question belongs to: Science chemistry

Question #969

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The Contact process is used for the manufacture of:

A. Sodium hydroxide

B. Ammonia

C. Sulphuric acid

D. Nitric acid

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Correct Answer: Option C

Explanation:
Contact process: SO₂ + O₂ ⇌ SO₃ (catalyst V₂O₅) followed by absorption in H₂SO₄ to produce H₂S₂O₇, then H₂SO₄.

This question belongs to: Science chemistry

Question #970

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Which of the following is used to remove grease stains from clothes?

A. Ethanol

B. Detergent

C. Vinegar

D. Sodium chloride

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Correct Answer: Option B

Explanation:
Detergents emulsify grease by forming micelles around oil droplets, removing them from fabric. Soap does same but less effective in hard water.

This question belongs to: Science chemistry

Question #971

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The setting time of cement is controlled by adding:

A. Gypsum

B. Clay

C. Sand

D. Limestone

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Correct Answer: Option A

Explanation:
Gypsum (CaSO₄·2H₂O) is added to clinker to slow down the rapid setting of C₃A, providing workable time. Without gypsum, flash set occurs.

This question belongs to: Science chemistry

Question #972

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Thermosetting plastics cannot be remolded because they:

A. Melt at high temperature

B. Have cross-linked structure

C. Are biodegradable

D. Are linear polymers

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Correct Answer: Option B

Explanation:
Thermosets (e.g., Bakelite) form extensive cross-links between polymer chains, making them rigid. Heating breaks bonds but degrades, not remolds. Thermoplastics are linear/branched.

This question belongs to: Science chemistry

Question #973

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Vulcanization of rubber uses:

A. Sulfur

B. Nitrogen

C. Carbon

D. Oxygen

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Correct Answer: Option A

Explanation:
Sulfur forms cross-links between polyisoprene chains, converting sticky raw rubber into strong, elastic material. Process discovered by Goodyear.

This question belongs to: Science chemistry

Question #974

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Which salt causes permanent hardness?

A. Mg(HCO₃)₂

B. CaSO₄

C. Na₂CO₃

D. Ca(HCO₃)₂

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Correct Answer: Option B

Explanation:
Calcium sulfate and magnesium sulfate/chloride cause permanent hardness. Bicarbonates cause temporary hardness removable by boiling.

This question belongs to: Science chemistry

Question #975

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Distillation is a method of purification that removes:

A. All microorganisms

B. Dissolved gases and volatile impurities

C. Suspended solids

D. Only color

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Correct Answer: Option B

Explanation:
Distillation involves boiling and condensation, separating non-volatile impurities (salts) and some volatile impurities. It can also kill microorganisms but boiling already does; distillation purifies further.

This question belongs to: Science chemistry

Question #976

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CFCs destroy ozone. Which atom is responsible?

A. Chlorine

B. Carbon

C. Fluorine

D. Oxygen

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Correct Answer: Option A

Explanation:
UV radiation releases chlorine atoms from CFCs; Cl catalytically decomposes O₃: Cl + O₃ → ClO + O₂; ClO + O → Cl + O₂. One Cl atom can destroy thousands of ozone molecules.

This question belongs to: Science chemistry

Question #977

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Gamma rays have no charge and no mass. They are:

A. Helium nuclei

B. Electromagnetic radiation

C. Particles

D. Electrons

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Correct Answer: Option B

Explanation:
Gamma rays are high-frequency electromagnetic waves emitted from the nucleus. They have very high penetration power and are used in cancer therapy.

This question belongs to: Science chemistry

Question #978

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If half-life of an element is 2 days, after 6 days fraction left is:

A. 1/8

B. 1/4

C. 1/2

D. 1/16

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Correct Answer: Option A

Explanation:
6/2 = 3 half-lives. Fraction = (1/2)³ = 1/8. Each half-life reduces remaining amount by half.

This question belongs to: Science chemistry

Question #979

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The neutron was discovered by James Chadwick. The particle used to bombard beryllium was:

A. Alpha particle

B. Gamma ray

C. Beta particle

D. Proton

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Correct Answer: Option A

Explanation:
Chadwick used alpha particles from polonium to bombard beryllium: ⁹Be + ⁴He → ¹²C + ¹n, producing neutrons.

This question belongs to: Science chemistry

Question #980

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Which of the following statements is correct regarding the Tyndall effect?

A. It is independent of the wavelength of light used.

B. It occurs due to scattering of light by colloidal particles.

C. It requires the particle size to be larger than the wavelength of light.

D. It is shown by true solutions.

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Correct Answer: Option B

Explanation:
The Tyndall effect is the scattering of a beam of light by a medium containing small suspended particles (like colloids). The particle size must be comparable to or smaller than the wavelength of light. True solutions do not show this effect because their particles are too small to scatter light effectively.

This question belongs to: Science chemistry

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