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Chemistry MCQs

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Hard fpsc Uploaded: 07 Aug 2026

What is the primary constituent of Portland cement?

A Calcium carbonate
B Calcium silicate
C Calcium oxide
D Calcium sulfate

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Correct Answer: Option B — Calcium silicate

Explanation: Calcium silicate compounds form the primary constituent of Portland cement, giving it strength when combined with water. This hydration reaction produces a hardened matrix used extensively in construction worldwide.

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Hard pms Uploaded: 07 Aug 2026

Which element is used as a moderator in nuclear reactors?

A Uranium
B Plutonium
C Graphite
D Cadmium

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Correct Answer: Option C — Graphite

Explanation: Graphite is commonly used as a moderator in nuclear reactors to slow down fast neutrons, increasing the probability of sustaining a controlled nuclear fission chain reaction without absorbing too many neutrons itself.

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Hard pms Uploaded: 07 Aug 2026

Which of these compounds is an example of an ester?

A Ethanol
B Ethanoic acid
C Ethyl ethanoate
D Ethylene

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Correct Answer: Option C — Ethyl ethanoate

Explanation: Ethyl ethanoate is an example of an ester, formed through the reaction between an alcohol and a carboxylic acid. Esters are known for their characteristic fruity smells and are widely used in flavorings and perfumes.

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Hard css fpsc ppsc Uploaded: 05 Aug 2026

Which element has the highest electronegativity of all elements on the Pauling scale?

A Fluorine
B Oxygen
C Chlorine
D Nitrogen

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Correct Answer: Option A — Fluorine

Explanation: Fluorine has the highest electronegativity of all elements at 3.98 on the Pauling scale due to its small atomic size and high effective nuclear charge attracting bonding electrons most strongly.

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Hard css fpsc Uploaded: 14 Jul 2026

Which element in Group 1 of the periodic table reacts most vigorously with water?

A Lithium
B Sodium
C Caesium
D Potassium

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Correct Answer: Option C — Caesium

Explanation: Caesium the heaviest stable Group 1 alkali metal reacts most vigorously with water due to its large atomic radius and low ionisation energy resulting in an explosive reaction.

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Hard css fpsc ppsc Uploaded: 14 Jul 2026

Which synthetic polymer was the first to be produced commercially and is used to make electrical fittings?

A Nylon
B PVC
C Bakelite
D Polythene

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Correct Answer: Option C — Bakelite

Explanation: Bakelite was the first commercially produced synthetic polymer made from phenol and formaldehyde in 1907 and is used in electrical fittings phone casings and kitchenware.

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Hard css Uploaded: 07 Aug 2026

What is the term used for the study of heat changes in chemical reactions?

A Electrochemistry
B Thermochemistry
C Photochemistry
D Stoichiometry

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Correct Answer: Option B — Thermochemistry

Explanation: Thermochemistry is the branch of chemistry that studies the heat energy associated with chemical reactions and physical transformations. It helps determine whether reactions are exothermic or endothermic based on enthalpy changes.

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Hard css Uploaded: 06 Aug 2026

What is Avogadro's number approximately equal to?

A 9.8 x 10^23
B 3.14 x 10^23
C 6.022 x 10^23
D 1.6 x 10^23

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Correct Answer: Option C — 6.022 x 10^23

Explanation: Avogadro's number, approximately 6.022 x 10^23, represents the number of particles in one mole of a substance. It is a fundamental constant used to convert between the atomic scale and macroscopic quantities in chemistry.

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Hard css fpsc Uploaded: 14 Jul 2026

Which law states that gases combine in simple whole number ratios by volume at the same temperature and pressure?

A Gay-Lussac's Law
B Boyle's Law
C Charles's Law
D Avogadro's Law

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Correct Answer: Option A — Gay-Lussac's Law

Explanation: Gay-Lussac's Law of Combining Volumes states that gases react in simple whole number ratios by volume at constant temperature and pressure providing evidence for atomic theory.

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Hard ppsc Uploaded: 06 Aug 2026

Which of the following is used as a catalyst in the Haber process?

A Platinum
B Iron
C Nickel
D Copper

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Correct Answer: Option B — Iron

Explanation: Iron acts as a catalyst in the Haber process, which combines nitrogen and hydrogen gases to produce ammonia. This industrial process is crucial for manufacturing fertilizers that support global agricultural production.

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Hard fpsc Uploaded: 06 Aug 2026

What is the standard unit of pressure in chemistry?

A Pascal
B Newton
C Joule
D Watt

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Correct Answer: Option A — Pascal

Explanation: The Pascal is the standard SI unit of pressure used in chemistry, defined as one newton per square meter. Pressure measurements are essential in understanding gas laws and reactions that occur under varying pressure conditions.

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Hard ppsc Uploaded: 06 Aug 2026

What is the molar mass of water approximately?

A 16 g/mol
B 20 g/mol
C 18 g/mol
D 22 g/mol

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Correct Answer: Option C — 18 g/mol

Explanation: Water has a molar mass of approximately 18 grams per mole, calculated by adding the atomic masses of two hydrogen atoms and one oxygen atom. This value is fundamental in stoichiometric calculations involving water.

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Hard css fpsc ppsc Uploaded: 14 Jul 2026

Which type of isomerism involves compounds with the same molecular formula but different structural arrangements?

A Structural isomerism
B Optical isomerism
C Geometric isomerism
D Dynamic isomerism

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Correct Answer: Option A — Structural isomerism

Explanation: Structural isomers have the same molecular formula but different connectivity of atoms leading to different structural arrangements and distinct physical and chemical properties.

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Hard css fpsc ppsc Uploaded: 14 Jul 2026

Which law states that the amount of substance deposited during electrolysis is directly proportional to the quantity of electricity passed?

A Boyle's Law
B Gay-Lussac's Law
C Avogadro's Law
D Faraday's First Law of Electrolysis

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Correct Answer: Option D — Faraday's First Law of Electrolysis

Explanation: Faraday's First Law of Electrolysis states that the mass of a substance deposited at an electrode during electrolysis is directly proportional to the quantity of charge passed.

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Hard css Uploaded: 07 Aug 2026

Which quantum number describes the shape of an orbital?

A Azimuthal quantum number
B Magnetic quantum number
C Spin quantum number
D Principal quantum number

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Correct Answer: Option A — Azimuthal quantum number

Explanation: The azimuthal quantum number, also called the angular momentum quantum number, determines the shape of an electron's orbital such as s, p, d, or f. It ranges in value from 0 to n-1 for a given energy level.

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Hard css Uploaded: 07 Aug 2026

Which of the following describes Le Chatelier's Principle?

A Reactions always favor products
B Systems at equilibrium resist changes to conditions
C Catalysts change equilibrium position
D Reactions cannot reach equilibrium

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Correct Answer: Option B — Systems at equilibrium resist changes to conditions

Explanation: Le Chatelier's Principle states that when a system at equilibrium experiences a change in concentration, temperature, or pressure, it shifts in the direction that counteracts the disturbance to restore a new equilibrium state.

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Hard css Uploaded: 07 Aug 2026

What is the empirical formula of benzene?

A C2H2
B C3H3
C C6H6
D CH

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Correct Answer: Option D — CH

Explanation: Benzene's molecular formula is C6H6, but its empirical formula simplifies to CH since the ratio of carbon to hydrogen atoms is 1:1. The empirical formula represents the simplest whole-number ratio of elements in a compound.

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Hard pms Uploaded: 06 Aug 2026

What is the primary use of sulfuric acid in industry?

A Textile dyeing
B Food preservation
C Water purification
D Fertilizer production

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Correct Answer: Option D — Fertilizer production

Explanation: Sulfuric acid is extensively used in the production of phosphate fertilizers, making it one of the most important industrial chemicals worldwide. It is also used in battery manufacturing, metal processing, and petroleum refining.

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Hard pms Uploaded: 07 Aug 2026

Which of the following elements is used in the vulcanization of rubber?

A Phosphorus
B Sulfur
C Silicon
D Carbon

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Correct Answer: Option B — Sulfur

Explanation: Sulfur is used in the vulcanization process to strengthen rubber by forming cross-links between polymer chains. This process, discovered by Charles Goodyear, significantly improves the durability and elasticity of rubber products.

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Hard ppsc Uploaded: 06 Aug 2026

What is the atomic mass unit based on?

A Hydrogen-1
B Oxygen-16
C Helium-4
D Carbon-12

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Correct Answer: Option D — Carbon-12

Explanation: The atomic mass unit is defined as one-twelfth the mass of a Carbon-12 atom. This standard allows scientists to compare the relative masses of different atoms and molecules consistently across the periodic table.

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