chemistry MCQs

Science

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.

1089
Total Questions

Practice Questions

Page 9 of 55
Question #161
The force that holds atoms together in a molecule is called:
A. Chemical bond
B. Nuclear force
C. Magnetic force
D. Gravitational force
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Chemical bonds are attractive forces between atoms due to electron interaction—ionic (transfer), covalent (sharing), metallic, etc. These bonds hold atoms together in molecules or crystals. Nuclear force holds protons and neutrons in nucleus. Gravitational and magnetic forces are negligible at atomic scale. Bond energy determines stability; stronger bond means more energy required to break.
This question belongs to: Science chemistry
Question #162
Which of the following is an electrovalent compound?
A. CCl₄
B. CO₂
C. KCl
D. CH₄
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
KCl (potassium chloride) is an ionic (electrovalent) compound formed by transfer of one electron from K to Cl, giving K⁺ and Cl⁻ ions held by electrostatic attraction. CH₄, CCl₄, CO₂ are covalent compounds with electron sharing. Electrovalent compounds have high melting points, conduct electricity in molten/aqueous state, and are generally soluble in water.
This question belongs to: Science chemistry
Question #163
In the modern periodic table, elements in the same group have the same:
A. Number of electron shells
B. Atomic mass
C. Number of isotopes
D. Number of valence electrons
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Elements in the same group (vertical column) have the same number of valence electrons, resulting in similar chemical properties. For example, all Group 1 elements have 1 valence electron (ns¹). The number of shells increases down the group. Atomic mass varies. This similarity was the basis for Mendeleev's grouping. Modern table uses atomic number for ordering.
This question belongs to: Science chemistry
Question #164
Ionization energy generally decreases down a group because:
A. Atomic radius increases and shielding effect increases
B. Number of valence electrons increases
C. Nuclear charge decreases
D. Electron affinity increases
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Down a group, number of shells increases, atomic radius increases, and inner electrons shield the outermost electron from the nucleus. The effective nuclear charge experienced by valence electron decreases, making it easier to remove. Thus ionization energy decreases. For example, IE of Cs
This question belongs to: Science chemistry
Question #165
The reaction N₂ + 3H₂ → 2NH₃ is an example of:
A. Combination reaction
B. Double displacement reaction
C. Displacement reaction
D. Decomposition reaction
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Two or more substances combine to form a single product: N₂ + 3H₂ → 2NH₃. This is a combination (synthesis) reaction. Decomposition involves a single compound breaking down. Displacement: one element displaces another. Double displacement: exchange of ions. The Haber process for ammonia is also a redox and reversible reaction. Combination can be exothermic.
This question belongs to: Science chemistry
Question #166
Which of the following is a redox reaction?
A. NaOH + HCl → NaCl + H₂O
B. CaCO₃ → CaO + CO₂
C. 2Na + Cl₂ → 2NaCl
D. BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
In 2Na + Cl₂ → 2NaCl, sodium is oxidized (Na → Na⁺ + e⁻) and chlorine is reduced (Cl₂ + 2e⁻ → 2Cl⁻). It involves change in oxidation states. Options A and B are double displacement (no change in oxidation states). Option D is decomposition with no change in oxidation states (Ca: +2 remains +2). Redox reactions involve simultaneous oxidation and reduction.
This question belongs to: Science chemistry
Question #167
Blue litmus turns red in a solution. The solution is likely:
A. Neutral
B. Saline
C. Acidic
D. Basic
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Acids turn blue litmus red; bases turn red litmus blue. Litmus is a purple dye extracted from lichens, used as an indicator. pH < 4.5 red, > 8.3 blue, intermediate purple. Neutral solution (pH 7) does not change the color of litmus significantly. This is a simple test for acid-base nature.
This question belongs to: Science chemistry
Question #168
Which of the following metals reacts with steam but not with cold water?
A. Calcium
B. Sodium
C. Potassium
D. Magnesium
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Magnesium reacts with hot water or steam to form MgO/Mg(OH)₂ and H₂, but very slowly with cold water (thin layer of insoluble hydroxide inhibits reaction). Sodium, potassium, and calcium react vigorously with cold water. Aluminium, zinc, iron react with steam but not cold water. Reactivity with water follows the series: K, Na, Ca (cold water); Mg, Al, Zn, Fe (steam).
This question belongs to: Science chemistry
Question #169
An alloy of mercury with another metal is called:
A. Brass
B. Amalgam
C. Solder
D. Bronze
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
An amalgam is an alloy of mercury with another metal. For example, sodium amalgam (used as reducing agent), zinc amalgam (for Clemmensen reduction), and dental amalgam (mercury-silver-tin-copper). Most metals dissolve in mercury, forming amalgams, except iron and platinum. Amalgams can be liquid or solid depending on proportion. Used in gold extraction.
This question belongs to: Science chemistry
Question #170
The allotrope of carbon used in electrodes and as a neutron moderator in nuclear reactors is:
A. Fullerene
B. Diamond
C. Charcoal
D. Graphite
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Graphite is used in electrodes (due to electrical conductivity) and as a moderator in nuclear reactors (to slow down neutrons). It is chemically stable and can withstand high temperatures. Diamond is an insulator. Fullerene is a nanomaterial. Charcoal is used as adsorbent and fuel. Graphite blocks are used in RBMK reactors (like Chernobyl) and in advanced gas-cooled reactors.
This question belongs to: Science chemistry
Question #171
Which hydrocarbon has the molecular formula C₃H₈?
A. Propane
B. Ethane
C. Methane
D. Butane
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Propane is an alkane with three carbon atoms: CH₃CH₂CH₃, formula C₃H₈. Methane: CH₄, Ethane: C₂H₆, Butane: C₄H₁₀. Propane is a component of LPG. Alkanes follow CnH₂n+2. For n=3, H=8. Propane is a gas at room temperature, liquefied under pressure. It is used as fuel for heating and cooking.
This question belongs to: Science chemistry
Question #172
The process of destructive distillation of coal yields:
A. Only methane
B. Coke, coal tar, and coal gas
C. Graphite
D. Petrol and diesel
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
Heating coal in the absence of air (destructive distillation) produces coke (solid residue, high carbon), coal tar (mixture of aromatic compounds), ammoniacal liquor, and coal gas (H₂, CH₄, CO). Coke is used in blast furnace. Coal tar is a source of aromatic chemicals and pitch. Coal gas was used for lighting historically.
This question belongs to: Science chemistry
Question #173
Biofuels are derived from:
A. Minerals
B. Nuclear reactions
C. Fossil fuels
D. Biological materials (plants, waste)
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Biofuels are produced from biomass—recently living organisms or their metabolic byproducts. Examples: ethanol from sugarcane/corn, biodiesel from vegetable oils, biogas from organic waste. They are renewable and can reduce greenhouse gas emissions compared to fossil fuels. However, large-scale production may compete with food crops. Algae-based biofuels are also being researched.
This question belongs to: Science chemistry
Question #174
In electroplating, the object to be plated is made the:
A. Electrolyte
B. Cathode
C. Salt bridge
D. Anode
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
In electroplating, the object to be electroplated is connected as the cathode, where metal cations in the electrolyte are reduced to metal atoms and deposited as a coating. The anode is usually the plating metal, which oxidizes and dissolves, replenishing the electrolyte. For example, silver plating: cathode is the article, anode is pure silver, electrolyte is AgCN/AgNO₃.
This question belongs to: Science chemistry
Question #175
A gas at 300 K occupies 2 L. If the temperature is raised to 600 K at constant pressure, the volume becomes:
A. 4 L
B. 1 L
C. 6 L
D. 2 L
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Charles' law: V₁/T₁ = V₂/T₂. V₂ = V₁ × T₂/T₁ = 2 L × 600 K / 300 K = 4 L. Volume doubles as absolute temperature doubles. Note: must use Kelvin, not Celsius. (600 K = 327°C). If mass and pressure are constant, volume is directly proportional to absolute temperature.
This question belongs to: Science chemistry
Question #176
Which of the following is NOT a characteristic of an ideal gas?
A. Obeys PV = nRT at all conditions
B. No intermolecular forces
C. Particles have no volume
D. Particles have strong attractive forces
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Ideal gas assumptions: particles have negligible volume, no intermolecular forces, and elastic collisions. Real gases deviate due to finite molecular size and attractions. At high pressure and low temperature, real gases deviate significantly; van der Waals equation corrects. So having strong attractive forces is not an ideal gas property. Ideal gas law PV = nRT is a limiting law.
This question belongs to: Science chemistry
Question #177
Enzyme catalysts are highly specific. This property is called:
A. Optimum temperature
B. Denaturation
C. Inhibition
D. Substrate specificity
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Enzymes exhibit substrate specificity, meaning each enzyme catalyzes a particular reaction or acts on a specific substrate (lock-and-key model). For example, urease acts only on urea. This specificity is due to the unique shape of the active site. Denaturation is loss of structure, inhibition is blocking activity, optimum temperature is condition for maximum activity.
This question belongs to: Science chemistry
Question #178
Vanadium(V) oxide is used as a catalyst in the manufacture of:
A. Sulphuric acid
B. Nitric acid
C. Sodium hydroxide
D. Ammonia
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
V₂O₅ catalyzes the oxidation of SO₂ to SO₃ in the Contact process for sulfuric acid: 2SO₂ + O₂ ⇌ 2SO₃. Fe is used for ammonia (Haber). Pt-Rh gauze for nitric acid (Ostwald). Sodium hydroxide is made by chlor-alkali electrolysis, no catalyst needed. V₂O₅ is preferred over Pt because it is cheaper and less susceptible to poisoning by arsenic impurities.
This question belongs to: Science chemistry
Question #179
The process of heating an ore in the absence of air to remove volatile impurities is called:
A. Leaching
B. Smelting
C. Calcination
D. Roasting
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Calcination involves heating an ore in limited supply or absence of air, often to convert carbonates/hydroxides to oxides and remove moisture or volatile impurities. Example: CaCO₃ → CaO + CO₂; Al(OH)₃ → Al₂O₃ + 3H₂O. Roasting is heating in excess air, usually for sulfide ores. Smelting uses reducing agents to obtain metal. Leaching uses chemicals.
This question belongs to: Science chemistry
Question #180
Which of the following is a biofertilizer that fixes atmospheric nitrogen in symbiotic association with legumes?
A. Pseudomonas
B. Rhizobium
C. Azotobacter
D. Azospirillum
Discuss
Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
Rhizobium bacteria form root nodules in leguminous plants (peas, beans, clover) and fix atmospheric N₂ into ammonia, providing nitrogen to the plant, while the plant supplies carbohydrates. Azotobacter and Azospirillum are free-living nitrogen fixers. Pseudomonas is a general soil bacterium. Symbiotic association is mutualistic. Inoculating seeds with Rhizobium culture increases soil fertility.
This question belongs to: Science chemistry

More Science Topics

Biology MCQs
Physics MCQs
Today's Top Topics
Biology 2054 Physics 1287 chemistry 1089
Explore Subjects
Computer 5279 Maths 5575 Accountancy and Statistics 3179 Science 4430 Static General Knowledge 6362
Practice Mix
Which of the following describes a precompiled collection of SQL statements stored on the database server that can be executed repeatedly by name?
Which major corporate computing entity was founded directly from the evolution of Herman Hollerith’s Tabulating Machine Company?
Total Fertility Rate (TFR) of 2.5 indicates that, on average, women are having:
Choose the antonym of 'YEARNING'.
The median of the dataset: 10, 15, 20, 25, 30, 35 is: