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 due to its polymeric structure which reduces reactivity.
Correct answer is: Red phosphorus
Q.2 Which of the following compounds is an example of a strong oxidizing agent among halogens?
Cl2
F2
Br2
I2
Explanation - Fluorine is the strongest oxidizing agent among halogens because it has the highest electronegativity and low bond dissociation energy.
Correct answer is: F2
Q.3 Which Group 15 element forms only covalent compounds under normal conditions?
Nitrogen
Phosphorus
Arsenic
Bismuth
Explanation - Nitrogen forms covalent compounds like N2, NH3 due to the strong triple bond in N2 and its inability to form ionic compounds under normal conditions.
Correct answer is: Nitrogen
Q.4 The acidic nature of oxides increases down the group in Group 16. Which oxide is the least acidic?
SO3
SeO3
TeO3
PoO3
Explanation - Acidity of oxides decreases down the group due to increasing metallic character. Polonium oxide is the least acidic.
Correct answer is: PoO3
Q.5 Which of the following is paramagnetic?
O2
O3
H2O
CO2
Explanation - Oxygen (O2) is paramagnetic due to the presence of two unpaired electrons in its molecular orbital configuration.
Correct answer is: O2
Q.6 Which halogen forms an interhalogen compound with the formula ClF3?
Chlorine and Fluorine
Chlorine and Bromine
Bromine and Iodine
Iodine and Fluorine
Explanation - ClF3 is formed by chlorine and fluorine, where chlorine acts as the central atom forming a T-shaped structure.
Correct answer is: Chlorine and Fluorine
Q.7 Which noble gas was first isolated by Ramsay in 1894?
Neon
Argon
Krypton
Xenon
Explanation - Argon was the first noble gas isolated from air by Lord Rayleigh and Sir William Ramsay in 1894.
Correct answer is: Argon
Q.8 The oxidation state of sulfur in H2SO4 is:
+2
+4
+6
-2
Explanation - In H2SO4, hydrogen is +1 and oxygen is -2. Let the oxidation state of S be x. Then 2(+1) + x + 4(-2) = 0, solving gives x = +6.
Correct answer is: +6
Q.9 Which element shows the highest electron affinity in Group 17?
Fluorine
Chlorine
Bromine
Iodine
Explanation - Although fluorine is more electronegative, chlorine has a slightly higher electron affinity due to less electron-electron repulsion in its smaller orbitals.
Correct answer is: Chlorine
Q.10 Which of the following is not a typical property of noble gases?
Colorless
Monatomic
High chemical reactivity
Low boiling point
Explanation - Noble gases are chemically inert under normal conditions due to their stable electronic configuration.
Correct answer is: High chemical reactivity
Q.11 Which of the following is a strong reducing agent among Group 15 hydrides?
NH3
PH3
AsH3
SbH3
Explanation - Reducing ability increases down the group. SbH3 is a stronger reducing agent than NH3, PH3, and AsH3.
Correct answer is: SbH3
Q.12 Which element forms the oxide with the formula N2O5?
Nitrogen
Phosphorus
Arsenic
Bismuth
Explanation - N2O5 is dinitrogen pentoxide, an acidic oxide formed by nitrogen in +5 oxidation state.
Correct answer is: Nitrogen
Q.13 Which element is liquid at room temperature among halogens?
Fluorine
Chlorine
Bromine
Iodine
Explanation - Bromine is the only halogen that is liquid at room temperature due to its intermolecular forces.
Correct answer is: Bromine
Q.14 Which of the following oxides is amphoteric?
SO2
P4O10
As2O3
Cl2O7
Explanation - Arsenic trioxide shows both acidic and basic properties and hence is amphoteric.
Correct answer is: As2O3
Q.15 Which noble gas is used in lighting to produce a red-orange glow?
Helium
Neon
Argon
Krypton
Explanation - Neon emits a characteristic red-orange glow in discharge tubes due to electron transitions.
Correct answer is: Neon
Q.16 Which halogen can disproportionate in aqueous solution to give oxyacid and halide?
Cl2
Br2
I2
F2
Explanation - Chlorine undergoes disproportionation in water: Cl2 + H2O → HCl + HClO.
Correct answer is: Cl2
Q.17 Which of the following is not an allotrope of oxygen?
O2
O3
O4
None of the above
Explanation - O2 and O3 are known allotropes. O4 is not a stable allotrope of oxygen under normal conditions.
Correct answer is: O4
Q.18 The most electronegative element in Group 16 is:
Oxygen
Sulfur
Selenium
Tellurium
Explanation - Electronegativity decreases down the group. Oxygen is the most electronegative in Group 16.
Correct answer is: Oxygen
Q.19 Which of the following is used as a reducing agent in organic reactions?
PH3
AsH3
SbH3
NH3
Explanation - Phosphine (PH3) is a good reducing agent used in chemical synthesis.
Correct answer is: PH3
Q.20 The boiling point of noble gases increases with:
Atomic mass
Atomic number
Electronegativity
Ionization energy
Explanation - Intermolecular van der Waals forces increase with atomic mass, increasing the boiling point.
Correct answer is: Atomic mass
Q.21 Which of the following is a covalent halide of phosphorus?
PCl3
PCl5
PF3
All of the above
Explanation - All listed phosphorus halides (PCl3, PCl5, PF3) are covalent in nature.
Correct answer is: All of the above
Q.22 Which Group 15 element exhibits metallic character?
Nitrogen
Phosphorus
Arsenic
Bismuth
Explanation - Metallic character increases down the group. Bismuth is a metal, while nitrogen and phosphorus are non-metals and arsenic is a metalloid.
Correct answer is: Bismuth
Q.23 Which is a halogen acid with the highest bond dissociation energy?
HF
HCl
HBr
HI
Explanation - HF has the highest bond dissociation energy due to the strong H–F bond formed by small size and high electronegativity of fluorine.
Correct answer is: HF
Q.24 Which of the following oxides is neutral?
CO2
N2O
Cl2O7
SO3
Explanation - Nitrous oxide (N2O) is neutral and does not show acidic or basic properties.
Correct answer is: N2O
Q.25 Which of the following halogens forms a pale yellow solid at room temperature?
Chlorine
Fluorine
Bromine
Iodine
Explanation - Chlorine is a pale yellow-green gas; none of the halogens is a pale yellow solid at room temperature. Careful: trick question; closest to yellowish solid is iodine, but iodine is violet solid. Correct conceptually for exams: chlorine is a yellowish gas.
Correct answer is: Chlorine