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 48 of 55
Question #941
Which of the following plastics is used for making non-stick cookware?
A. PVC
B. Nylon
C. Polystyrene
D. Teflon
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Correct Answer: Option D

Explanation:
Teflon (PTFE) has low friction and high heat stability, ideal for non-stick coatings. PVC for pipes; polystyrene for packaging; nylon for fibers.
This question belongs to: Science chemistry
Question #942
Soap is prepared by the reaction of fats with:
A. NaOH
B. HCl
C. NaCl
D. Ethanol
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Correct Answer: Option A

Explanation:
Saponification: fat + NaOH → soap + glycerol. This is an alkaline hydrolysis. NaCl is used to precipitate soap (salting out).
This question belongs to: Science chemistry
Question #943
Hard water contains dissolved:
A. Ammonium salts
B. Sodium salts
C. Calcium and magnesium salts
D. Potassium salts
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Correct Answer: Option C

Explanation:
Hardness is caused by Ca²⁺ and Mg²⁺ ions in the form of bicarbonates, sulfates, chlorides. They react with soap to form scum.
This question belongs to: Science chemistry
Question #944
Ozonation in water treatment is better than chlorination because it:
A. Adds minerals
B. Is cheaper
C. Leaves no harmful residue
D. Is easier to store
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Correct Answer: Option C

Explanation:
Ozone decomposes to O₂, leaving no residual taste or toxic by-products like trihalomethanes. However, it must be generated on-site and is more expensive.
This question belongs to: Science chemistry
Question #945
Global warming is caused by the trapping of:
A. Infrared radiation
B. X-rays
C. Visible light
D. UV rays
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Correct Answer: Option A

Explanation:
Greenhouse gases absorb outgoing infrared radiation from Earth, trapping heat and warming the atmosphere. Ozone absorbs UV; global warming is primarily IR.
This question belongs to: Science chemistry
Question #946
Beta particles are emitted from the nucleus. They are:
A. Helium nuclei
B. Protons
C. Fast electrons
D. Neutrons
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Correct Answer: Option C

Explanation:
Beta (β⁻) particles are high-energy electrons emitted when a neutron converts to a proton. Positrons (β⁺) are also beta particles.
This question belongs to: Science chemistry
Question #947
The time taken for a radioactive substance to reduce to half its initial amount is:
A. Full-life
B. Half-life
C. Dosage
D. Mean life
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Correct Answer: Option B

Explanation:
Half-life (T₁/₂) is the characteristic time for radioactive decay. For first-order kinetics, it is constant.
This question belongs to: Science chemistry
Question #948
Rutherford used which particles in his gold foil experiment?
A. Neutrons
B. Alpha particles
C. Beta particles
D. Gamma rays
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Correct Answer: Option B

Explanation:
Rutherford bombarded a thin gold foil with alpha particles. Most passed through, but some were deflected, leading to the nuclear model.
This question belongs to: Science chemistry
Question #949
Which of the following changes is a physical change?
A. Curdling of milk
B. Burning of coal
C. Boiling of water
D. Rusting of iron
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Correct Answer: Option C

Explanation:
Boiling water changes state from liquid to gas, but the chemical composition (H₂O) remains unchanged – physical change. Others form new substances.
This question belongs to: Science chemistry
Question #950
The technique of chromatography is used for:
A. Separating immiscible liquids
B. Separating solids from liquids
C. Separating dissolved substances by differential adsorption
D. Boiling point separation
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Correct Answer: Option C

Explanation:
Chromatography separates components of a mixture based on their different affinities for stationary and mobile phases. Used for dyes, drugs, amino acids.
This question belongs to: Science chemistry
Question #951
Atomic number of sodium is 11. Its electronic configuration is:
A. 2,7,2
B. 2,8,8
C. 2,8,1
D. 2,8,2
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Correct Answer: Option C

Explanation:
Na (Z=11): K=2, L=8, M=1. Hence 2,8,1. One valence electron makes it Group 1, Period 3.
This question belongs to: Science chemistry
Question #952
The number of protons in ¹⁸O is:
A. 10
B. 8
C. 18
D. 16
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Correct Answer: Option B

Explanation:
Oxygen atomic number is 8, thus 8 protons. Isotope ¹⁸O has 8 protons + 10 neutrons = 18 mass number.
This question belongs to: Science chemistry
Question #953
Which of the following has a triple bond?
A. Benzene
B. Ethene
C. Ethyne
D. Ethane
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Correct Answer: Option C

Explanation:
Ethyne (C₂H₂) has a carbon-carbon triple bond (HC≡CH). Ethene has double; ethane single; benzene has delocalized pi bonds.
This question belongs to: Science chemistry
Question #954
The horizontal rows in the periodic table are called:
A. Families
B. Periods
C. Groups
D. Blocks
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Correct Answer: Option B

Explanation:
Periods are horizontal rows (7 periods). Groups are vertical columns (18). Elements in same period have same number of electron shells.
This question belongs to: Science chemistry
Question #955
Ionization energy decreases down a group because:
A. Shells are removed
B. Electron affinity increases
C. Nuclear charge decreases
D. Shielding effect and atomic size increase
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Correct Answer: Option D

Explanation:
Down a group, atomic radius increases and inner shells shield the valence electron, reducing effective nuclear attraction, making electron removal easier.
This question belongs to: Science chemistry
Question #956
Which reaction is Fe₂O₃ + 3CO → 2Fe + 3CO₂?
A. Both B and C
B. Displacement
C. Combination
D. Redox
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Correct Answer: Option A

Explanation:
CO removes oxygen from Fe₂O₃ – it's a redox reaction. Also, CO displaces Fe, making it a displacement. So both redox and displacement.
This question belongs to: Science chemistry
Question #957
The term reduction refers to:
A. Gain of hydrogen
B. Loss of oxygen
C. Gain of electrons
D. All of the above
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Correct Answer: Option D

Explanation:
Reduction can be defined as loss of oxygen, gain of hydrogen, gain of electrons, or decrease in oxidation number. All are correct definitions.
This question belongs to: Science chemistry
Question #958
The pH of human blood is approximately:
A. 9
B. 7.4
C. 5.5
D. 2
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Correct Answer: Option B

Explanation:
Blood pH is slightly alkaline, maintained between 7.35 and 7.45. Deviation can cause acidosis or alkalosis.
This question belongs to: Science chemistry
Question #959
Which salt is used in the manufacture of soap?
A. Sodium carbonate
B. Sodium bicarbonate
C. Sodium hydroxide
D. Sodium chloride
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Correct Answer: Option C

Explanation:
Soap is made by saponification using NaOH (for hard soap) or KOH (for soft soap). NaCl is used to precipitate soap; Na₂CO₃ is washing soda.
This question belongs to: Science chemistry
Question #960
Galvanization protects iron by:
A. Providing a barrier only
B. Forming an alloy
C. Making iron more reactive
D. Sacrificial protection by a more reactive metal
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Correct Answer: Option D

Explanation:
Zinc coating (galvanizing) provides both barrier and sacrificial protection. Even if scratched, zinc corrodes instead of iron because it is more reactive.
This question belongs to: Science chemistry

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