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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Page 19 of 55
Question #361
The catalyst used in the hydrogenation of oils is:
A. Vanadium pentoxide
B. Platinum
C. Nickel
D. Iron
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Correct Answer: Option C

Explanation:
Nickel (finely divided) catalyzes the addition of hydrogen to unsaturated vegetable oils to form solid vanaspati ghee. It provides surface for reaction. Platinum and palladium also work but are expensive. Iron is used in Haber process. V₂O₅ in Contact process.
This question belongs to: Science chemistry
Question #362
The main ore of aluminium is:
A. Cinnabar
B. Bauxite
C. Haematite
D. Galena
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Correct Answer: Option B

Explanation:
Bauxite (Al₂O₃·2H₂O) is the principal ore of aluminium. Haematite is Fe₂O₃, galena is PbS, cinnabar is HgS. Bauxite is refined by Bayer's process to produce alumina, then electrolytically reduced (Hall-Héroult process).
This question belongs to: Science chemistry
Question #363
Urea contains what percentage of nitrogen approximately?
A. 46%
B. 35%
C. 21%
D. 15%
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Correct Answer: Option A

Explanation:
Urea (NH₂CONH₂) has molar mass 60, with 28 g N, percentage = (28/60)×100 ≈ 46.6%. Rounded to 46%. It is the most concentrated solid nitrogen fertilizer. Ammonium nitrate is 33%, ammonium sulfate 21%.
This question belongs to: Science chemistry
Question #364
Aqua regia is a mixture of:
A. HNO₃ and H₂SO₄
B. HF and HCl
C. HCl and HNO₃ in 3:1 ratio
D. HCl and H₂SO₄
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Correct Answer: Option C

Explanation:
Aqua regia (royal water) is a 3:1 mixture of concentrated HCl and HNO₃. It can dissolve noble metals gold and platinum by forming complex ions. Freshly prepared, it is a fuming yellow liquid. Used in etching and cleaning.
This question belongs to: Science chemistry
Question #365
Which of the following is an alloy of copper and tin?
A. Duralumin
B. Brass
C. Bronze
D. Steel
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Correct Answer: Option C

Explanation:
Bronze is an alloy primarily of copper and tin, sometimes with other elements. Brass is Cu-Zn. Steel is Fe-C. Duralumin is Al-Cu-Mg-Mn. Bronze is used for statues, coins, and bearings.
This question belongs to: Science chemistry
Question #366
The compound CH₃CH₂OH is commonly known as:
A. Propanol
B. Butanol
C. Ethanol
D. Methanol
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Correct Answer: Option C

Explanation:
CH₃CH₂OH is ethyl alcohol or ethanol. Methanol is CH₃OH. Propanol C₃H₇OH. Butanol C₄H₉OH. Ethanol is the active ingredient in alcoholic beverages and used as biofuel.
This question belongs to: Science chemistry
Question #367
Soap is prepared by heating fat with:
A. Ethanol
B. HCl
C. NaCl solution
D. NaOH solution
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Correct Answer: Option D

Explanation:
Soap is made by saponification: fat/oil (triglyceride) + NaOH → glycerol + sodium salt of fatty acid (soap). This is an alkaline hydrolysis. HCl would break down differently. NaCl is used to precipitate soap (salting out). Ethanol is solvent.
This question belongs to: Science chemistry
Question #368
Which of the following is NOT a property of metals?
A. Malleability
B. Brittleness
C. Good conductivity
D. Ductility
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Correct Answer: Option B

Explanation:
Metals are malleable (can be beaten into sheets), ductile (drawn into wires), and good conductors. Brittleness is a characteristic of non-metals and some metalloids; metals can deform without breaking. For example, gold is highly malleable.
This question belongs to: Science chemistry
Question #369
The process of converting sugar into alcohol by yeast is called:
A. Esterification
B. Hydrogenation
C. Saponification
D. Fermentation
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Correct Answer: Option D

Explanation:
Fermentation is the anaerobic breakdown of glucose by enzymes (zymase) in yeast to produce ethanol and CO₂: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. Esterification forms esters, saponification makes soap, hydrogenation adds H₂.
This question belongs to: Science chemistry
Question #370
The metal present in chlorophyll is:
A. Magnesium
B. Calcium
C. Iron
D. Sodium
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Correct Answer: Option A

Explanation:
Chlorophyll, the green pigment in plants, contains a magnesium ion (Mg²⁺) at the center of the porphyrin ring. It's essential for photosynthesis. Haemoglobin in blood contains iron. Calcium is in bones. Sodium is in body fluids.
This question belongs to: Science chemistry
Question #371
Which of the following is a thermoplastic?
A. Melamine
B. Vulcanized rubber
C. Polythene
D. Bakelite
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Correct Answer: Option C

Explanation:
Polythene (polyethylene) softens on heating and can be remolded, thus thermoplastic. Bakelite and melamine are thermosetting (cannot be remolded). Vulcanized rubber is also thermoset due to cross-linking. Thermoplastics have linear or branched chains, no cross-links.
This question belongs to: Science chemistry
Question #372
Which gas is produced when calcium carbonate reacts with dilute HCl?
A. Chlorine
B. Oxygen
C. Hydrogen
D. Carbon dioxide
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Correct Answer: Option D

Explanation:
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑. Carbon dioxide turns limewater milky. This is a test for carbonates and bicarbonates. The reaction is used in laboratory preparation of CO₂.
This question belongs to: Science chemistry
Question #373
The chemical name of plaster of Paris is:
A. Calcium sulphate hemihydrate
B. Calcium carbonate
C. Calcium oxide
D. Calcium sulphate dihydrate
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Correct Answer: Option A

Explanation:
Plaster of Paris is CaSO₄·½H₂O. It is made by heating gypsum (CaSO₄·2H₂O) at 373 K. It sets with water to form gypsum again. Used for plastering fractured bones, making statues.
This question belongs to: Science chemistry
Question #374
Which of the following statements about diamond is true?
A. It is the hardest natural substance
B. It is a good lubricant
C. It has a layered structure
D. It conducts electricity
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Correct Answer: Option A

Explanation:
Diamond has a rigid 3D covalent network, making it the hardest natural material. It does not conduct electricity (no free electrons). It is not layered (graphite is). It is used as an abrasive, not a lubricant.
This question belongs to: Science chemistry
Question #375
The main constituent of CNG is:
A. Butane
B. Propane
C. Methane
D. Ethane
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Correct Answer: Option C

Explanation:
CNG (Compressed Natural Gas) is primarily methane (CH₄). LPG is propane and butane. Methane is the lightest hydrocarbon. CNG is a cleaner fuel for vehicles.
This question belongs to: Science chemistry
Question #376
Calorific value is measured in:
A. g/cm³
B. L/mol
C. kJ/kg or J/g
D. °C
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Correct Answer: Option C

Explanation:
Calorific value is the heat produced by combustion of unit mass, expressed in energy per mass: kJ/kg, J/g, kcal/kg. Higher CV means better fuel. Determined by bomb calorimeter.
This question belongs to: Science chemistry
Question #377
In an electrolytic cell, oxidation takes place at the:
A. Anode
B. Electrolyte
C. Cathode
D. Salt bridge
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Correct Answer: Option A

Explanation:
In both electrolytic and galvanic cells, oxidation occurs at the anode (AN OX). The anode is positive in electrolytic cells, negative in galvanic. Reduction at cathode (RED CAT). Electroplating: object at cathode, dissolution at anode.
This question belongs to: Science chemistry
Question #378
According to Graham's law, the rate of diffusion of a gas is inversely proportional to the square root of its:
A. Density (or molar mass)
B. Temperature
C. Volume
D. Pressure
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Correct Answer: Option A

Explanation:
Graham's law: r ∝ 1/√M (molar mass). At same T,P, rate inversely proportional to square root of density. Lighter gases diffuse faster. Used in uranium enrichment (UF₆).
This question belongs to: Science chemistry
Question #379
The catalyst used in the manufacture of ammonia by Haber process is:
A. Pt
B. Fe
C. Ni
D. V₂O₅
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Correct Answer: Option B

Explanation:
Haber process: N₂ + 3H₂ ⇌ 2NH₃ using finely divided iron catalyst with promoters (K₂O, Al₂O₃). Pt in Ostwald for HNO₃, V₂O₅ in Contact for H₂SO₄, Ni in hydrogenation.
This question belongs to: Science chemistry
Question #380
Which of the following is a method of concentration of sulphide ores?
A. Calcination
B. Froth flotation
C. Magnetic separation
D. Smelting
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Correct Answer: Option B

Explanation:
Froth flotation is used for sulphide ores (ZnS, PbS, CuFeS₂). Ore particles adhere to oil froth and float, gangue sinks. Magnetic separation for magnetic ores. Calcination and smelting are extraction steps, not concentration.
This question belongs to: Science chemistry

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