Chemistry MCQs

Question #1021

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The main ore of copper is:

A. Copper pyrites

B. Haematite

C. Cinnabar

D. Bauxite

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Correct Answer: Option A

Explanation:
Copper pyrites, also known as chalcopyrite, is the most important and abundant ore of copper. Its chemical formula is CuFeS2. Bauxite is the ore of aluminum, cinnabar is the ore of mercury, and haematite is the primary ore of iron.

This question belongs to: Science chemistry

Question #1022

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Which of the following non-metals is lustrous?

A. Carbon

B. Phosphorus

C. Sulphur

D. Iodine

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Correct Answer: Option D

Explanation:
Luster is a characteristic physical property of metals, but some non-metals also exhibit a shiny appearance. Iodine is a non-metal that forms dark purple, lustrous crystalline solids. Sulphur is dull yellow, phosphorus is white/red and waxy, and carbon (as graphite/coal) is generally dull.

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Question #1023

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Consider the following statements: 1. Galvanization involves coating iron with zinc. 2. Sacrificial protection uses a more reactive metal to protect iron. Which is/are correct?

A. 2 only

B. Both 1 and 2

C. Neither 1 nor 2

D. 1 only

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Correct Answer: Option B

Explanation:
Galvanization is the process of applying a protective zinc coating to iron to prevent rusting. Sacrificial protection (or cathodic protection) involves connecting iron to a more reactive metal (like magnesium or zinc). The more reactive metal oxidizes preferentially, sacrificing itself to protect the iron. Both statements are correct.

This question belongs to: Science chemistry

Question #1024

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The IUPAC name of the compound CH3-CH(CH3)-CH2-CH3 is:

A. Isopentane

B. 2-ethylpropane

C. 2-methylbutane

D. 3-methylbutane

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Correct Answer: Option C

Explanation:
To name this alkane, find the longest continuous carbon chain, which has 4 carbons (butane). Number the chain from the end closest to the substituent to give it the lowest possible number. The methyl group is on the second carbon. Thus, the IUPAC name is 2-methylbutane. Isopentane is its common name.

This question belongs to: Science chemistry

Question #1025

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Which of the following is an unsaturated hydrocarbon?

A. Methane

B. Cyclohexane

C. Propane

D. Benzene

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Correct Answer: Option D

Explanation:
Unsaturated hydrocarbons contain at least one double or triple bond between carbon atoms. Benzene (C6H6) has a ring structure with alternating double bonds (delocalized pi electrons), making it highly unsaturated. Cyclohexane, propane, and methane contain only single bonds and are saturated hydrocarbons.

This question belongs to: Science chemistry

Question #1026

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The functional group present in aldehydes is:

A. -COOH

B. -CO-

C. -OH

D. -CHO

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Correct Answer: Option D

Explanation:
Aldehydes are organic compounds containing the formyl group, -CHO, where a carbon atom is double-bonded to an oxygen atom and single-bonded to a hydrogen atom. -OH is the hydroxyl group (alcohols), -COOH is the carboxyl group (carboxylic acids), and -CO- is the carbonyl group (ketones).

This question belongs to: Science chemistry

Question #1027

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Assertion (A): Ethene decolorizes bromine water. Reason (R): Ethene undergoes an addition reaction with bromine.

A. A is true but R is false.

B. Both A and R are true but R is NOT the correct explanation of A.

C. Both A and R are true and R is the correct explanation of A.

D. A is false but R is true.

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Correct Answer: Option C

Explanation:
Ethene (C2H4) is an alkene containing a reactive carbon-carbon double bond. When bromine water (brown) is added to ethene, the double bond breaks and bromine atoms add across it to form 1,2-dibromoethane (colorless). This addition reaction decolorizes the bromine water, serving as a test for unsaturation.

This question belongs to: Science chemistry

Question #1028

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Which of the following is the main component of natural gas?

A. Methane

B. Butane

C. Propane

D. Ethane

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Correct Answer: Option A

Explanation:
Natural gas is a fossil fuel composed primarily of methane (CH4), typically making up 70-90% of its volume. It also contains smaller amounts of ethane, propane, butane, and other heavier hydrocarbons, along with non-hydrocarbon gases like carbon dioxide and nitrogen.

This question belongs to: Science chemistry

Question #1029

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The process of breaking down large hydrocarbon molecules into smaller, more useful ones by heating is called:

A. Cracking

B. Alkylation

C. Polymerization

D. Reforming

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Correct Answer: Option A

Explanation:
Cracking is a petrochemical process where complex, heavy hydrocarbon molecules are broken down (cleaved) into lighter, more valuable molecules like gasoline and alkenes. This is achieved by applying high temperatures and pressures, often in the presence of a catalyst (catalytic cracking).

This question belongs to: Science chemistry

Question #1030

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Consider the following statements: 1. Biofuels are renewable energy sources. 2. Biodiesel is produced by the transesterification of vegetable oils. Which is/are correct?

A. 2 only

B. Neither 1 nor 2

C. 1 only

D. Both 1 and 2

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Correct Answer: Option D

Explanation:
Biofuels, such as bioethanol and biodiesel, are derived from recent biological materials (biomass) and can be replenished, making them renewable. Biodiesel is specifically produced through transesterification, a chemical reaction where vegetable oils or animal fats react with an alcohol (like methanol) to form fatty acid methyl esters.

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Question #1031

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Which gas is known as 'marsh gas'?

A. Ethane

B. Propane

C. Methane

D. Butane

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Correct Answer: Option C

Explanation:
Methane (CH4) is commonly known as marsh gas because it is produced by the anaerobic decomposition of organic matter in swamps and marshes by methanogenic bacteria. It is also the primary component of biogas and natural gas.

This question belongs to: Science chemistry

Question #1032

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LPG is domesticated with a strong-smelling compound to detect leaks. This compound is:

A. Ethanol

B. Chloroform

C. Methanol

D. Thioethanol

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Correct Answer: Option D

Explanation:
LPG (Liquefied Petroleum Gas) is naturally odorless. To detect dangerous leaks, a strong-smelling sulfur compound called ethyl mercaptan (thioethanol, C2H5SH) is added to it. Its pungent, rotting-cabbage-like smell is easily detectable by the human nose even at very low concentrations.

This question belongs to: Science chemistry

Question #1033

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In an electrolytic cell, oxidation occurs at the:

A. Anode

B. Cathode

C. Electrolyte

D. Salt bridge

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Correct Answer: Option A

Explanation:
In any electrochemical cell, the anode is defined as the electrode where oxidation (loss of electrons) takes place, and the cathode is where reduction (gain of electrons) occurs. In an electrolytic cell, the anode is positively charged, attracting anions which then lose electrons.

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Question #1034

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Which of the following is used as the electrolyte in a lead-acid storage battery?

A. Phosphoric acid

B. Nitric acid

C. Sulphuric acid

D. Hydrochloric acid

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Correct Answer: Option C

Explanation:
A lead-acid battery, commonly used in automobiles, consists of lead anodes and lead dioxide cathodes. The electrolyte used is an aqueous solution of sulfuric acid (H2SO4). During discharge, the acid is consumed to form lead sulfate and water, decreasing the density of the electrolyte.

This question belongs to: Science chemistry

Question #1035

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Assertion (A): Sodium chloride conducts electricity in its molten state. Reason (R): In the molten state, the ions are free to move and carry charge.

A. A is true but R is false.

B. Both A and R are true and R is the correct explanation of A.

C. Both A and R are true but R is NOT the correct explanation of A.

D. A is false but R is true.

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Correct Answer: Option B

Explanation:
Sodium chloride is an ionic compound. In the solid state, its Na+ and Cl- ions are held tightly in a crystal lattice and cannot move, so it doesn't conduct. When melted, the lattice breaks down, and the ions become mobile. These free-moving ions carry the electric current, making it a good conductor.

This question belongs to: Science chemistry

Question #1036

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The mass of a substance deposited at the cathode is directly proportional to the:

A. Current

B. All of the above

C. Quantity of electricity passed

D. Time

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Correct Answer: Option B

Explanation:
According to Faraday's First Law of Electrolysis, the mass (m) of a substance deposited at an electrode is directly proportional to the total quantity of electricity (Q) passed through the electrolyte. Since Q = Current (I) × Time (t), the mass is directly proportional to both the current and the time.

This question belongs to: Science chemistry

Question #1037

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Which of the following is a primary battery?

A. Lead-acid battery

B. Lithium-ion battery

C. Dry cell

D. Nickel-Cadmium battery

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Correct Answer: Option C

Explanation:
Primary batteries are non-rechargeable; the chemical reaction that produces electricity cannot be reversed. The common dry cell (zinc-carbon battery) and alkaline batteries are primary cells. Lead-acid, Ni-Cd, and Li-ion are secondary (rechargeable) batteries where the reaction can be reversed by applying an external current.

This question belongs to: Science chemistry

Question #1038

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Consider the following statements: 1. Specific conductance decreases with dilution. 2. Equivalent conductance increases with dilution. Which is/are correct?

A. Neither 1 nor 2

B. 1 only

C. 2 only

D. Both 1 and 2

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Correct Answer: Option D

Explanation:
Specific conductance (conductivity) is the conductance of a 1 cm³ solution. It decreases with dilution because the number of ions per unit volume decreases. Equivalent conductance is the conductance of all ions produced by 1 gram equivalent of electrolyte. It increases with dilution because the ions have more space to move, reducing interionic attractions.

This question belongs to: Science chemistry

Question #1039

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The root mean square (rms) velocity of a gas is given by the formula:

A. √(3P/d)

B. √(8RT/πM)

C. Both A and B

D. √(3RT/M)

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Correct Answer: Option C

Explanation:
The root mean square velocity (urms) of gas molecules can be expressed in multiple equivalent ways. It is √(3RT/M) where R is the gas constant, T is temperature, and M is molar mass. Since P = dRT/M (where d is density), it can also be written as √(3P/d). Both formulas are correct.

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Question #1040

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Which of the following gases deviates most from ideal behavior at room temperature?

A. Ammonia

B. Helium

C. Hydrogen

D. Nitrogen

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Correct Answer: Option A

Explanation:
Real gases deviate from ideal behavior due to intermolecular forces and molecular volume. Ammonia (NH3) has strong intermolecular hydrogen bonding and a relatively large molecular size compared to small, non-polar gases like He, H2, and N2. Therefore, ammonia exhibits the greatest deviation from ideal gas behavior.

This question belongs to: Science chemistry

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