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 #1061
The Solvay process is used for the manufacture of:
A. Nitric acid
B. Sodium carbonate
C. Ammonia
D. Sulfuric acid
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Correct Answer: Option B

Explanation:
The Solvay process (or ammonia-soda process) is the major industrial process for the production of sodium carbonate (soda ash, Na2CO3). It uses brine (NaCl) and limestone (CaCO3) as raw materials, with ammonia acting as an intermediate that is recovered and recycled.
This question belongs to: Science chemistry
Question #1062
The process of vulcanization of rubber was invented by:
A. Hermann Staudinger
B. Wallace Carothers
C. Leo Baekeland
D. Charles Goodyear
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Correct Answer: Option D

Explanation:
Vulcanization is the chemical process of converting natural rubber or related polymers into more durable materials by adding sulfur or other equivalent curatives. This process was discovered by Charles Goodyear in 1839, revolutionizing the rubber industry by making it less sticky and more temperature-resistant.
This question belongs to: Science chemistry
Question #1063
Bakelite is a polymer of:
A. Ethylene
B. Phenol and formaldehyde
C. Vinyl chloride
D. Tetrafluoroethylene
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Correct Answer: Option B

Explanation:
Bakelite, the first fully synthetic plastic, is a thermosetting phenol formaldehyde resin. It is formed by a condensation reaction between phenol and formaldehyde. Once molded and heated, it sets permanently and cannot be remelted. It is used for electrical switches, utensil handles, and jewelry.
This question belongs to: Science chemistry
Question #1064
Terylene is also known as:
A. Polyacrylonitrile
B. Nylon
C. Polyester
D. Polyurethane
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Correct Answer: Option C

Explanation:
Terylene is a synthetic fiber belonging to the polyester family. Chemically, it is polyethylene terephthalate (PET), formed by the condensation polymerization of ethylene glycol and terephthalic acid. It is widely used in textiles, plastic bottles, and recording tapes.
This question belongs to: Science chemistry
Question #1065
The main constituent of biogas (gobar gas) is:
A. Ethane
B. Propane
C. Methane
D. Butane
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Correct Answer: Option C

Explanation:
Biogas, commonly known as gobar gas in India, is produced by the anaerobic digestion of organic waste (like cattle dung) by methanogenic bacteria. The primary component of biogas is methane (CH4), which typically makes up 50-75% of the gas mixture, along with carbon dioxide and trace gases.
This question belongs to: Science chemistry
Question #1066
Which of the following is a water-soluble vitamin?
A. Vitamin A
B. Vitamin K
C. Vitamin D
D. Vitamin C
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Correct Answer: Option D

Explanation:
Vitamins are classified into fat-soluble (A, D, E, K) and water-soluble (B-complex and C) groups. Vitamin C (ascorbic acid) is water-soluble, meaning it dissolves in water and is not stored in the body to a significant extent, requiring regular dietary intake. Vitamins A, D, and K are fat-soluble.
This question belongs to: Science chemistry
Question #1067
The chemical name of Vitamin C is:
A. Tocopherol
B. Ascorbic acid
C. Calciferol
D. Retinol
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Correct Answer: Option B

Explanation:
Vitamin C is chemically known as ascorbic acid (C6H8O6). It is a vital nutrient involved in the repair of tissue and the enzymatic production of certain neurotransmitters. Deficiency leads to scurvy. Retinol is Vitamin A, Calciferol is Vitamin D, and Tocopherol is Vitamin E.
This question belongs to: Science chemistry
Question #1068
Which of the following is an example of a broad-spectrum antibiotic?
A. Penicillin
B. Chloramphenicol
C. Streptomycin
D. Amoxicillin
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Correct Answer: Option B

Explanation:
Broad-spectrum antibiotics are effective against a wide range of bacteria, including both Gram-positive and Gram-negative species. Chloramphenicol is a classic example of a broad-spectrum antibiotic. Penicillin is generally narrow-spectrum, primarily targeting Gram-positive bacteria.
This question belongs to: Science chemistry
Question #1069
The temporary hardness of water is caused by the presence of:
A. Chlorides of calcium and magnesium
B. Nitrates of calcium and magnesium
C. Sulfates of calcium and magnesium
D. Bicarbonates of calcium and magnesium
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Correct Answer: Option D

Explanation:
Water hardness is classified into temporary and permanent. Temporary hardness is caused by the dissolved bicarbonates of calcium and magnesium (Ca(HCO3)2 and Mg(HCO3)2). It is called 'temporary' because it can be easily removed by simple boiling, which decomposes the soluble bicarbonates into insoluble carbonates.
This question belongs to: Science chemistry
Question #1070
The permanent hardness of water can be removed by adding:
A. Baking soda
B. Washing soda
C. Soda ash
D. Caustic soda
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Correct Answer: Option B

Explanation:
Permanent hardness is caused by dissolved chlorides and sulfates of calcium and magnesium. It cannot be removed by boiling. It is removed by adding washing soda (sodium carbonate, Na2CO3). The carbonate ions react with the soluble calcium and magnesium salts to form insoluble carbonates, which precipitate out.
This question belongs to: Science chemistry
Question #1071
Calgon is used for water softening. Its chemical name is:
A. Sodium hexametaphosphate
B. Sodium silicate
C. Sodium aluminate
D. Sodium zeolite
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Correct Answer: Option A

Explanation:
Calgon is the trade name for sodium hexametaphosphate (Na6P6O18). It is used to soften hard water because the hexametaphosphate ion binds (chelates) with calcium and magnesium ions in the water, forming a soluble complex. This prevents the metal ions from interfering with soap lathering.
This question belongs to: Science chemistry
Question #1072
Heavy water (D2O) is used as a:
A. Fuel
B. Solvent for organic compounds
C. Moderator in nuclear reactors
D. Coolant in refrigerators
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Correct Answer: Option C

Explanation:
Heavy water (D2O) contains deuterium (an isotope of hydrogen) instead of normal hydrogen. It has a higher molecular mass and absorbs neutrons much less efficiently than ordinary water. Because of this property, it is extensively used as a neutron moderator in certain types of nuclear reactors (like CANDU) to slow down neutrons.
This question belongs to: Science chemistry
Question #1073
Which of the following gases is responsible for the depletion of the ozone layer?
A. Sulfur dioxide
B. Methane
C. Chlorofluorocarbons (CFCs)
D. Carbon dioxide
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Correct Answer: Option C

Explanation:
Chlorofluorocarbons (CFCs), once widely used as refrigerants and propellants, are the primary culprits behind ozone depletion. When CFCs reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms. A single chlorine atom can catalytically destroy thousands of ozone (O3) molecules.
This question belongs to: Science chemistry
Question #1074
The pH of acid rain is typically less than:
A. 4.0
B. 7.0
C. 6.5
D. 5.6
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Correct Answer: Option D

Explanation:
Normal rainwater is slightly acidic (pH ~5.6) due to the dissolution of atmospheric CO2 forming carbonic acid. Acid rain is defined as precipitation with a pH lower than 5.6. It is caused by emissions of sulfur dioxide and nitrogen oxides, which react with water to form stronger sulfuric and nitric acids.
This question belongs to: Science chemistry
Question #1075
The biological oxygen demand (BOD) of clean water is typically:
A. Between 10 and 20 ppm
B. Greater than 500 ppm
C. Between 50 and 100 ppm
D. Less than 5 ppm
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Correct Answer: Option D

Explanation:
Biological Oxygen Demand (BOD) measures the amount of dissolved oxygen needed by aerobic organisms to break down organic material in water. Clean, unpolluted water has a low BOD, typically less than 5 ppm. Highly polluted water can have a BOD of 17 ppm or much higher, indicating severe organic contamination.
This question belongs to: Science chemistry
Question #1076
Which of the following is an example of green chemistry?
A. Using CFCs as refrigerants.
B. Using hydrogen peroxide for bleaching paper.
C. Using chlorine for bleaching paper.
D. Using leaded gasoline.
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Correct Answer: Option B

Explanation:
Green chemistry aims to design products and processes that minimize the use and generation of hazardous substances. Using hydrogen peroxide (H2O2) for bleaching paper is an example of green chemistry because it breaks down into harmless water and oxygen, unlike chlorine which can produce toxic, persistent organochlorine byproducts.
This question belongs to: Science chemistry
Question #1077
The half-life of a radioactive isotope is 10 years. What fraction of the original sample will remain after 30 years?
A. 1/16
B. 1/8
C. 1/4
D. 1/2
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Correct Answer: Option B

Explanation:
The half-life is the time required for half of the radioactive atoms to decay. After 10 years (1 half-life), 1/2 remains. After 20 years (2 half-lives), 1/4 remains. After 30 years (3 half-lives), the fraction remaining is (1/2)^3 = 1/8. Thus, one-eighth of the original sample will remain.
This question belongs to: Science chemistry
Question #1078
Which of the following rays has the maximum penetrating power?
A. Alpha rays
B. Gamma rays
C. Beta rays
D. X-rays
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Correct Answer: Option B

Explanation:
Radioactive decay emits alpha, beta, and gamma rays. Alpha particles are heavy and positively charged, stopped by paper. Beta particles are lighter, stopped by aluminum. Gamma rays are high-energy electromagnetic photons with no mass or charge, giving them the highest penetrating power; they require thick lead or concrete to be significantly attenuated.
This question belongs to: Science chemistry
Question #1079
Carbon-14 is used in:
A. Treatment of cancer
B. Radiocarbon dating
C. Generating nuclear power
D. Tracing blood clots
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Correct Answer: Option B

Explanation:
Carbon-14 is a radioactive isotope of carbon with a half-life of about 5,730 years. It is continuously formed in the atmosphere and incorporated into living organisms. When the organism dies, C-14 decays. By measuring the remaining C-14, scientists can determine the age of archaeological and geological samples up to ~50,000 years old.
This question belongs to: Science chemistry
Question #1080
Which of the following is NOT a natural radioactive series?
A. Thorium series
B. Actinium series
C. Neptunium series
D. Uranium series
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Correct Answer: Option C

Explanation:
There are three naturally occurring radioactive decay series: the Uranium series (4n+2), the Thorium series (4n), and the Actinium series (4n+3). The Neptunium series (4n+1) is an artificial series; its longest-lived isotope, Neptunium-237, has a half-life too short to have survived since the Earth's formation.
This question belongs to: Science chemistry

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