Q.1 Which of the following is the most stable allotrope of phosphorus at room temperature?
White phosphorus
Red phosphorus
Black phosphorus
Violet phosphorus
Explanation - Red phosphorus is more stable than white phosphorus at room temperature because it has a polymeric structure, reducing reactivity.
Correct answer is: Red phosphorus
Q.2 Which element is commonly used in the manufacture of semiconductors?
Arsenic
Phosphorus
Antimony
Bismuth
Explanation - Arsenic is used in semiconductors, particularly in gallium arsenide (GaAs), due to its electronic properties.
Correct answer is: Arsenic
Q.3 Which of the following halogens is the strongest oxidizing agent?
Fluorine
Chlorine
Bromine
Iodine
Explanation - Fluorine is the strongest oxidizing agent due to its high electronegativity and small atomic size.
Correct answer is: Fluorine
Q.4 Which group 16 element is liquid at room temperature?
Oxygen
Sulfur
Selenium
Tellurium
Explanation - Oxygen is a diatomic gas at room temperature; none of group 16 elements are liquid at room temperature. Trick question: oxygen is not liquid but gas, other elements are solids.
Correct answer is: Oxygen
Q.5 The noble gas with the highest atomic number that is stable is:
Radon
Krypton
Xenon
Helium
Explanation - Radon (Rn, Z=86) is the heaviest stable (technically radioactive but long-lived) noble gas commonly found naturally.
Correct answer is: Radon
Q.6 Which element in group 15 exhibits +5 oxidation state most readily?
Nitrogen
Phosphorus
Arsenic
Bismuth
Explanation - Nitrogen forms stable compounds in +5 oxidation state (like HNO3), while heavier elements prefer lower oxidation states due to the inert pair effect.
Correct answer is: Nitrogen
Q.7 Which of the following compounds is used in fire retardants?
Phosphorus trichloride
Antimony trioxide
Arsenic trioxide
Bismuth nitrate
Explanation - Antimony trioxide (Sb2O3) is used in combination with halogenated compounds to make fire retardants.
Correct answer is: Antimony trioxide
Q.8 Which halogen forms a diatomic molecule at room temperature?
Fluorine
Chlorine
Bromine
All of the above
Explanation - All halogens (F2, Cl2, Br2, I2) exist as diatomic molecules in elemental form at room temperature, except astatine which is rare and solid.
Correct answer is: All of the above
Q.9 Which of the following is the heaviest stable halogen?
Chlorine
Bromine
Iodine
Astatine
Explanation - Iodine is the heaviest halogen that is sufficiently stable; astatine is radioactive and decays quickly.
Correct answer is: Iodine
Q.10 Which group 16 element is commonly used in vulcanization of rubber?
Oxygen
Sulfur
Selenium
Tellurium
Explanation - Sulfur forms cross-links in rubber during vulcanization, improving elasticity and strength.
Correct answer is: Sulfur
Q.11 Which noble gas is used in lighting applications due to its emission spectrum?
Neon
Argon
Krypton
Xenon
Explanation - Neon emits bright red-orange light when electrically excited, commonly used in neon signs.
Correct answer is: Neon
Q.12 Which of the following nitrogen compounds is commonly used as a fertilizer?
Ammonium nitrate
Nitric oxide
Nitrogen triiodide
Hydrazine
Explanation - Ammonium nitrate (NH4NO3) is widely used as a nitrogen-rich fertilizer.
Correct answer is: Ammonium nitrate
Q.13 Which halogen is liquid at room temperature?
Fluorine
Chlorine
Bromine
Iodine
Explanation - Bromine is the only halogen that exists as a liquid at room temperature, appearing reddish-brown.
Correct answer is: Bromine
Q.14 Which group 15 element is a metalloid?
Nitrogen
Phosphorus
Arsenic
Bismuth
Explanation - Arsenic exhibits properties of both metals and non-metals, making it a metalloid.
Correct answer is: Arsenic
Q.15 Which noble gas can form compounds under extreme conditions?
Neon
Argon
Krypton
Helium
Explanation - Krypton can form compounds like KrF2 under extreme conditions with fluorine.
Correct answer is: Krypton
Q.16 Which group 16 element is toxic in large amounts but essential in trace amounts?
Oxygen
Sulfur
Selenium
Tellurium
Explanation - Selenium is an essential trace element but can be toxic at higher doses.
Correct answer is: Selenium
Q.17 Which of the following phosphorus allotropes is highly reactive and stored under water?
White phosphorus
Red phosphorus
Black phosphorus
Violet phosphorus
Explanation - White phosphorus is highly reactive and ignites spontaneously in air, so it is stored under water.
Correct answer is: White phosphorus
Q.18 Which halogen is most likely to form hydrogen bonds with water?
Fluorine
Chlorine
Bromine
Iodine
Explanation - Fluorine is highly electronegative and forms strong hydrogen bonds with water.
Correct answer is: Fluorine
Q.19 Which group 15 element exhibits a strong inert pair effect?
Nitrogen
Phosphorus
Bismuth
Arsenic
Explanation - Bismuth shows inert pair effect strongly, preferring +3 oxidation state over +5.
Correct answer is: Bismuth
Q.20 Which noble gas is used in high-intensity discharge lamps?
Neon
Argon
Krypton
Xenon
Explanation - Xenon is used in HID lamps and flash lamps due to its ability to produce bright white light.
Correct answer is: Xenon
Q.21 Which oxygen allotrope is used as a disinfectant and bleaching agent?
O2
O3
Liquid O2
None of the above
Explanation - Ozone (O3) is a strong oxidizing agent used for disinfection and bleaching.
Correct answer is: O3
Q.22 Which halogen is commonly used in the preparation of PVC?
Fluorine
Chlorine
Bromine
Iodine
Explanation - Chlorine is used to produce vinyl chloride monomer (VCM), which is polymerized to make PVC.
Correct answer is: Chlorine
Q.23 Which group 16 element forms toxic hydrides known as 'chalcogen hydrides'?
Oxygen
Sulfur
Selenium
Tellurium
Explanation - Tellurium forms toxic hydrides (H2Te), which are highly unstable and poisonous.
Correct answer is: Tellurium
Q.24 Which group 15 element is used in the production of semiconductors and LEDs?
Nitrogen
Phosphorus
Arsenic
Antimony
Explanation - Gallium arsenide (GaAs) is a widely used semiconductor in LEDs, lasers, and integrated circuits.
Correct answer is: Arsenic
Q.25 Which halogen reacts violently with hydrogen at room temperature?
Fluorine
Chlorine
Bromine
Iodine
Explanation - Fluorine reacts explosively with hydrogen even at room temperature due to its extreme reactivity.
Correct answer is: Fluorine