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301. Which of the following best defines hydrogen bonding?
ⓐ. A type of covalent bond involving hydrogen and a metal
ⓑ. An intermolecular force caused by attraction between a hydrogen atom bonded to an electronegative atom and a lone pair on another electronegative atom
ⓒ. The sharing of hydrogen atoms between two nuclei equally
ⓓ. A purely ionic interaction involving hydrogen ions
Correct Answer: An intermolecular force caused by attraction between a hydrogen atom bonded to an electronegative atom and a lone pair on another electronegative atom
Explanation: Hydrogen bonding occurs when hydrogen is covalently bonded to a highly electronegative atom (like O, N, F) and interacts with the lone pair of another electronegative atom. This results in a strong dipole-dipole attraction that influences physical and chemical properties.
302. Which molecule is expected to form the strongest hydrogen bond?
ⓐ. H₂O
ⓑ. NH₃
ⓒ. HF
ⓓ. CH₄
Correct Answer: HF
Explanation: HF exhibits the strongest hydrogen bonding because fluorine is the most electronegative element and its small size allows for strong H–F···F interactions. While H₂O and NH₃ also form hydrogen bonds, CH₄ cannot because C–H bonds are non-polar and carbon lacks sufficient electronegativity.
303. What is the difference between intermolecular and intramolecular hydrogen bonding?
ⓐ. Intermolecular occurs within the same molecule, intramolecular occurs between different molecules
ⓑ. Intermolecular occurs between different molecules, intramolecular occurs within the same molecule
ⓒ. Both occur only in solids
ⓓ. Both are identical in nature and strength
Correct Answer: Intermolecular occurs between different molecules, intramolecular occurs within the same molecule
Explanation: **Intermolecular hydrogen bonding** (e.g., between H₂O molecules) is responsible for high boiling points. **Intramolecular hydrogen bonding** occurs within a single molecule (e.g., o-nitrophenol, where –OH forms a bond with –NO₂ group). This reduces intermolecular interactions and may lower boiling points.
304. Which compound shows intramolecular hydrogen bonding?
ⓐ. o-nitrophenol
ⓑ. p-nitrophenol
ⓒ. Methanol
ⓓ. Ammonia
Correct Answer: o-nitrophenol
Explanation: In o-nitrophenol, the –OH group can form a hydrogen bond with the adjacent –NO₂ group within the same molecule. This intramolecular bonding reduces intermolecular hydrogen bonding, so o-nitrophenol is more volatile than p-nitrophenol, which forms intermolecular H-bonds.
305. Why does water have an abnormally high boiling point compared to H₂S?
ⓐ. Because O–H bond is stronger than S–H bond
ⓑ. Because water forms extensive hydrogen bonding, while H₂S does not
ⓒ. Because oxygen is heavier than sulfur
ⓓ. Because water is ionic while H₂S is covalent
Correct Answer: Because water forms extensive hydrogen bonding, while H₂S does not
Explanation: Each water molecule can form up to 4 hydrogen bonds (2 donor, 2 acceptor). This intermolecular hydrogen bonding leads to a high boiling point. H₂S, despite being in the same group, does not form strong hydrogen bonds due to low electronegativity of sulfur.
306. Which of the following molecules does NOT form hydrogen bonds?
ⓐ. HF
ⓑ. NH₃
ⓒ. CH₄
ⓓ. H₂O
Correct Answer: CH₄
Explanation: CH₄ does not form hydrogen bonds because carbon is not sufficiently electronegative to create the required bond polarity, and it lacks lone pairs. In contrast, HF, NH₃, and H₂O have highly polar bonds and lone pairs that enable hydrogen bonding.
307. Which of the following is a consequence of hydrogen bonding in liquids?
ⓐ. Decreased viscosity
ⓑ. Lower boiling points
ⓒ. Abnormally high boiling points and surface tension
ⓓ. Absence of intermolecular forces
Correct Answer: Abnormally high boiling points and surface tension
Explanation: Hydrogen bonding greatly strengthens intermolecular attraction. As a result, compounds like H₂O, HF, and NH₃ have higher boiling points and surface tension than expected from molecular mass alone. This explains anomalies like water remaining liquid at room temperature.
308. Why is ice less dense than liquid water?
ⓐ. Because hydrogen bonding is weaker in ice
ⓑ. Because hydrogen bonding forces molecules into an open hexagonal lattice structure
ⓒ. Because water molecules contract upon freezing
ⓓ. Because ice contains no hydrogen bonds
Correct Answer: Because hydrogen bonding forces molecules into an open hexagonal lattice structure
Explanation: In ice, each water molecule forms four hydrogen bonds, creating a rigid open lattice with large empty spaces. This lowers density, making ice float on water. When ice melts, some hydrogen bonds break, and water molecules pack more closely.
309. Which molecule exhibits stronger hydrogen bonding: NH₃ or H₂O?
ⓐ. NH₃, because it has more hydrogens
ⓑ. H₂O, because oxygen is more electronegative and can form more hydrogen bonds per molecule
ⓒ. Both equal, since they are group hydrides
ⓓ. Neither, since both are covalent
Correct Answer: H₂O, because oxygen is more electronegative and can form more hydrogen bonds per molecule
Explanation: Oxygen is more electronegative than nitrogen, creating stronger O–H···O hydrogen bonds. Moreover, each water molecule can form up to four H-bonds, while NH₃ can form fewer due to having only one lone pair. Thus, hydrogen bonding is stronger in water.
310. Which type of hydrogen bonding increases the volatility of a compound?
ⓐ. Intermolecular hydrogen bonding
ⓑ. Intramolecular hydrogen bonding
ⓒ. Metallic hydrogen bonding
ⓓ. Ionic hydrogen bonding
Correct Answer: Intramolecular hydrogen bonding
Explanation: Intramolecular hydrogen bonding reduces the extent of intermolecular interactions. For example, o-nitrophenol forms intramolecular H-bonds, lowering its boiling point and increasing volatility compared to p-nitrophenol, which forms intermolecular hydrogen bonds.
311. Which of the following best describes intermolecular hydrogen bonding?
ⓐ. Hydrogen bond formed within a single molecule
ⓑ. Hydrogen bond formed between different molecules of the same or different substances
ⓒ. Bonding between hydrogen and metal atoms
ⓓ. A purely covalent interaction without polarity
Correct Answer: Hydrogen bond formed between different molecules of the same or different substances
Explanation: Intermolecular hydrogen bonding occurs when a hydrogen atom covalently attached to an electronegative atom (like O, N, F) interacts with a lone pair on another molecule. This explains high boiling points of substances such as water and hydrogen fluoride.
312. Which is the best example of intermolecular hydrogen bonding?
ⓐ. o-nitrophenol
ⓑ. p-nitrophenol
ⓒ. Acetone
ⓓ. Methane
Correct Answer: p-nitrophenol
Explanation: In p-nitrophenol, the –OH group forms hydrogen bonds with neighboring molecules instead of within the same molecule. This intermolecular hydrogen bonding increases boiling point and decreases volatility compared to o-nitrophenol, which has intramolecular H-bonding.
313. Which compound shows intramolecular hydrogen bonding?
ⓐ. Ethanol
ⓑ. p-nitrophenol
ⓒ. o-nitrophenol
ⓓ. Hydrogen fluoride
Correct Answer: o-nitrophenol
Explanation: In o-nitrophenol, the hydroxyl group forms a hydrogen bond with the nitro group within the same molecule. This intramolecular hydrogen bonding reduces intermolecular attractions, making o-nitrophenol more volatile and less soluble in water compared to p-nitrophenol.
314. What is the effect of intermolecular hydrogen bonding on boiling point?
ⓐ. It lowers the boiling point
ⓑ. It increases the boiling point
ⓒ. It has no effect on boiling point
ⓓ. It makes the compound unstable
Correct Answer: It increases the boiling point
Explanation: Intermolecular hydrogen bonds hold molecules together strongly, requiring more energy to separate them. This leads to higher boiling points in compounds like water, HF, and NH₃ compared to similar-sized molecules without hydrogen bonding.
315. What is the effect of intramolecular hydrogen bonding on solubility in water?
ⓐ. Increases solubility
ⓑ. Decreases solubility
ⓒ. No effect on solubility
ⓓ. Completely prevents solubility
Correct Answer: Decreases solubility
Explanation: Intramolecular hydrogen bonding reduces the ability of a molecule to form hydrogen bonds with water molecules. For example, o-nitrophenol (intramolecular H-bonding) is less soluble in water than p-nitrophenol (intermolecular H-bonding).
316. Which of the following compounds will have the lowest boiling point due to intramolecular hydrogen bonding?
ⓐ. Water
ⓑ. Ethanol
ⓒ. o-nitrophenol
ⓓ. p-nitrophenol
Correct Answer: o-nitrophenol
Explanation: Intramolecular hydrogen bonding in o-nitrophenol reduces intermolecular forces between molecules. This makes it more volatile and lowers its boiling point compared to p-nitrophenol, which has intermolecular hydrogen bonding.
317. Why does o-hydroxybenzaldehyde show intramolecular hydrogen bonding?
ⓐ. Because –OH group bonds with an external molecule
ⓑ. Because –OH group forms a hydrogen bond with the aldehyde oxygen within the same molecule
ⓒ. Because it has very low electronegativity
ⓓ. Because aldehyde group prevents hydrogen bonding
Correct Answer: Because –OH group forms a hydrogen bond with the aldehyde oxygen within the same molecule
Explanation: In o-hydroxybenzaldehyde, the –OH group is ortho to the –CHO group. The hydrogen from –OH interacts with the oxygen of the aldehyde within the same molecule, forming intramolecular H-bonding. This stabilizes a ring-like structure.
318. Intermolecular hydrogen bonding is mainly responsible for:
ⓐ. Decreased viscosity of liquids
ⓑ. Low surface tension
ⓒ. High boiling point and high viscosity
ⓓ. Ionic character of bonds
Correct Answer: High boiling point and high viscosity
Explanation: Intermolecular hydrogen bonds link molecules strongly, creating resistance to flow (viscosity) and requiring high energy for separation (boiling point). This explains why water and glycerol exhibit high viscosity and boiling points.
319. Which of the following pairs correctly illustrates both types of hydrogen bonding?
ⓐ. Water (intermolecular), o-nitrophenol (intramolecular)
ⓑ. Methane (intermolecular), benzene (intramolecular)
ⓒ. Ethanol (intramolecular), CO₂ (intermolecular)
ⓓ. Ammonia (intramolecular), HF (intramolecular)
Correct Answer: Water (intermolecular), o-nitrophenol (intramolecular)
Explanation: Water molecules form intermolecular hydrogen bonds with each other, explaining its anomalous properties. o-Nitrophenol forms intramolecular hydrogen bonds between –OH and –NO₂ groups within the same molecule.
320. Which type of hydrogen bonding usually increases the volatility of a compound?
ⓐ. Intermolecular hydrogen bonding
ⓑ. Intramolecular hydrogen bonding
ⓒ. Metallic hydrogen bonding
ⓓ. Ionic hydrogen bonding
Correct Answer: Intramolecular hydrogen bonding
Explanation: Intramolecular H-bonding prevents molecules from associating strongly with one another. This reduces intermolecular attractions, lowering boiling point and increasing volatility, as seen in o-nitrophenol compared to p-nitrophenol.
321. Why does H₂O exhibit extensive hydrogen bonding?
ⓐ. Because oxygen has low electronegativity
ⓑ. Because each water molecule can form up to four hydrogen bonds
ⓒ. Because hydrogen atoms are very large in size
ⓓ. Because water molecules are linear
Correct Answer: Because each water molecule can form up to four hydrogen bonds
Explanation: Oxygen in H₂O has two lone pairs, and each hydrogen can form one H-bond. Thus, one water molecule can form four hydrogen bonds in total (2 donors, 2 acceptors). This extensive hydrogen bonding network explains the unusually high boiling point, high specific heat, and liquid state of water at room temperature.
322. Which property of water is primarily due to hydrogen bonding?
ⓐ. Its molecular mass
ⓑ. Its colorless nature
ⓒ. Its anomalously high boiling and melting points
ⓓ. Its covalent O–H bonds
Correct Answer: Its anomalously high boiling and melting points
Explanation: Compounds of similar molecular mass (like H₂S) are gases at room temperature, but H₂O is liquid. This anomaly is explained by strong intermolecular hydrogen bonding in water, which requires large amounts of energy to break.
323. Which type of hydrogen bonding is present in HF?
ⓐ. Only intramolecular
ⓑ. Only intermolecular
ⓒ. Both intermolecular and intramolecular
ⓓ. None, as HF is purely covalent
Correct Answer: Only intermolecular
Explanation: In HF, hydrogen bonds are formed between the highly polar H–F groups of different HF molecules. These strong intermolecular H-bonds cause HF to exist as a liquid with abnormally high boiling point compared to other hydrogen halides.
324. Why does HF have a much higher boiling point than HCl, HBr, and HI?
ⓐ. Because fluorine is heavier than other halogens
ⓑ. Because HF has strong intermolecular hydrogen bonding
ⓒ. Because HF has the weakest covalent bond
ⓓ. Because HF is an ionic compound
Correct Answer: Because HF has strong intermolecular hydrogen bonding
Explanation: HF molecules are strongly associated through H-bonds due to the high electronegativity and small size of fluorine. The other hydrogen halides lack significant hydrogen bonding, so their boiling points follow normal van der Waals trends.
325. Why is NH₃ less strongly hydrogen-bonded than H₂O?
ⓐ. Because nitrogen is less electronegative than oxygen and has only one lone pair
ⓑ. Because NH₃ has no lone pairs available for bonding
ⓒ. Because H–N bonds are purely ionic
ⓓ. Because nitrogen has a higher atomic mass
Correct Answer: Because nitrogen is less electronegative than oxygen and has only one lone pair
Explanation: Each NH₃ molecule can form only one H-bond donor per hydrogen, but with only one lone pair, fewer acceptor sites are available compared to water. As a result, hydrogen bonding in NH₃ is weaker and less extensive.
326. Which molecule shows the strongest hydrogen bonding among H₂O, NH₃, and HF?
ⓐ. H₂O
ⓑ. NH₃
ⓒ. HF
ⓓ. All equal
Correct Answer: HF
Explanation: Although H₂O forms the largest network of hydrogen bonds, the individual H–F···F bonds are the strongest due to fluorine’s very high electronegativity and small atomic size. This makes hydrogen bonding in HF stronger than in H₂O or NH₃.
327. Which hydrogen-bonded system explains why DNA strands are held together?
ⓐ. O–H···O bonds
ⓑ. N–H···O and N–H···N hydrogen bonds between base pairs
ⓒ. H–F···F bonds
ⓓ. Ionic bonding between phosphate groups
Correct Answer: N–H···O and N–H···N hydrogen bonds between base pairs
Explanation: In DNA, complementary base pairs (adenine–thymine and guanine–cytosine) are linked by hydrogen bonds. A–T has two hydrogen bonds, while G–C has three. These intermolecular H-bonds provide stability yet allow strand separation during replication.
328. Which of the following molecules is liquid at room temperature mainly due to hydrogen bonding?
ⓐ. NH₃
ⓑ. HF
ⓒ. H₂O
ⓓ. CH₄
Correct Answer: H₂O
Explanation: Despite its low molecular mass, water is liquid at room temperature. This is due to its ability to form an extensive three-dimensional network of intermolecular hydrogen bonds, unlike NH₃ (weaker H-bonds), HF (smaller network), or CH₄ (no H-bonding).
329. Why is the boiling point of ethanol higher than that of dimethyl ether, though both have the same molecular formula (C₂H₆O)?
ⓐ. Because ethanol has stronger covalent bonds
ⓑ. Because ethanol forms intermolecular hydrogen bonds, while ether cannot
ⓒ. Because ethers are nonpolar compounds
ⓓ. Because ethanol has higher molecular mass
Correct Answer: Because ethanol forms intermolecular hydrogen bonds, while ether cannot
Explanation: Ethanol has an –OH group, which can donate and accept hydrogen bonds, raising its boiling point. Dimethyl ether lacks a hydrogen directly bonded to oxygen, so it cannot form hydrogen bonds with itself, leading to lower boiling point.
330. Which of the following is the correct order of hydrogen bonding strength?
ⓐ. NH₃ < H₂O < HF
ⓑ. HF < NH₃ < H₂O
ⓒ. H₂O < NH₃ < HF
ⓓ. NH₃ < HF < H₂O
Correct Answer: NH₃ < H₂O < HF
Explanation: Hydrogen bonding strength depends on electronegativity and lone pair availability. NH₃ has weaker H-bonds due to lower electronegativity of nitrogen. H₂O has stronger H-bonds because oxygen is more electronegative and can form four bonds. HF has the strongest H-bonds due to the extreme electronegativity of fluorine and high bond polarity.
331. Which factor makes hydrogen bonding in HF stronger than in NH₃?
ⓐ. HF has more hydrogen atoms per molecule
ⓑ. Fluorine is more electronegative and smaller than nitrogen
ⓒ. HF is a non-polar molecule
ⓓ. NH₃ has no lone pairs available for bonding
Correct Answer: Fluorine is more electronegative and smaller than nitrogen
Explanation: The strength of hydrogen bonding depends on bond polarity and atomic size. In HF, the H–F bond is highly polar because fluorine is the most electronegative element. Its small size also concentrates charge, making H–F···F hydrogen bonds very strong compared to N–H···N hydrogen bonds in NH₃.
332. Which anomalous property of water is directly explained by hydrogen bonding?
ⓐ. Water is colorless
ⓑ. Ice floats on liquid water
ⓒ. Water is a universal solvent
ⓓ. Water has a low molecular mass
Correct Answer: Ice floats on liquid water
Explanation: In ice, each H₂O molecule forms four hydrogen bonds, creating an open hexagonal lattice with empty spaces. This makes ice less dense than liquid water, where hydrogen bonds partially break and molecules pack more closely. As a result, ice floats on water, an anomaly explained by hydrogen bonding.
333. Which hydrogen-bonding feature explains the unusually high surface tension of water?
ⓐ. Weak intermolecular forces
ⓑ. Extensive network of intermolecular hydrogen bonds
ⓒ. Presence of ionic impurities in water
ⓓ. Covalent O–H bonds within water molecules
Correct Answer: Extensive network of intermolecular hydrogen bonds
Explanation: Surface tension arises from strong cohesive forces at the liquid’s surface. In water, intermolecular hydrogen bonding holds molecules tightly, increasing surface tension. This property allows insects like water striders to walk on water.
334. In NH₃, hydrogen bonding is weaker than in H₂O because:
ⓐ. N–H bonds are ionic in nature
ⓑ. Nitrogen has fewer lone pairs and lower electronegativity than oxygen
ⓒ. NH₃ has more hydrogen atoms than oxygen
ⓓ. NH₃ cannot form intermolecular interactions
Correct Answer: Nitrogen has fewer lone pairs and lower electronegativity than oxygen
Explanation: NH₃ has three N–H bonds but only one lone pair for accepting H-bonds. Oxygen in water has two lone pairs and higher electronegativity, enabling stronger and more extensive hydrogen bonding compared to ammonia.
335. Why does HF exhibit higher viscosity than HCl, HBr, or HI?
ⓐ. Because fluorine has the largest atomic radius
ⓑ. Because HF molecules are linked by strong hydrogen bonds
ⓒ. Because HF has lower molar mass
ⓓ. Because HF is a polar covalent liquid
Correct Answer: Because HF molecules are linked by strong hydrogen bonds
Explanation: HF molecules associate through strong H–F···F intermolecular hydrogen bonds, producing high viscosity. Other hydrogen halides (HCl, HBr, HI) lack significant hydrogen bonding, so they remain gases at room temperature and have much lower viscosities.
336. Which compound forms the largest number of hydrogen bonds per molecule?
ⓐ. HF
ⓑ. NH₃
ⓒ. H₂O
ⓓ. CH₄
Correct Answer: H₂O
Explanation: A single H₂O molecule can form four hydrogen bonds (two via hydrogen atoms as donors and two via lone pairs on oxygen as acceptors). HF and NH₃ can form fewer hydrogen bonds, while CH₄ does not form hydrogen bonds at all.
337. Which hydrogen bonding pattern is essential for the secondary structure of proteins (α-helix, β-sheet)?
ⓐ. N–H···O hydrogen bonds
ⓑ. H–F···F hydrogen bonds
ⓒ. O–H···Cl hydrogen bonds
ⓓ. Metallic hydrogen bonding
Correct Answer: N–H···O hydrogen bonds
Explanation: In proteins, hydrogen bonding occurs between the N–H group of one peptide bond and the C=O group of another. This N–H···O bonding stabilizes α-helices and β-pleated sheets, which are crucial for protein folding.
338. Which of the following explains why glycerol (C₃H₅(OH)₃) is highly viscous?
ⓐ. It is a heavy molecule
ⓑ. It contains three –OH groups per molecule capable of extensive hydrogen bonding
ⓒ. It is non-polar and forms ionic interactions
ⓓ. It contains carbonyl groups
Correct Answer: It contains three –OH groups per molecule capable of extensive hydrogen bonding
Explanation: Each glycerol molecule has three hydroxyl groups, allowing strong intermolecular hydrogen bonding with neighboring molecules. This extensive hydrogen bonding network makes glycerol highly viscous and gives it a high boiling point.
339. Why does ethanol (C₂H₅OH) mix completely with water in all proportions?
ⓐ. Because ethanol is non-polar
ⓑ. Because ethanol forms intermolecular hydrogen bonds with water molecules
ⓒ. Because ethanol has higher density than water
ⓓ. Because ethanol lacks polarity
Correct Answer: Because ethanol forms intermolecular hydrogen bonds with water molecules
Explanation: The –OH group in ethanol forms hydrogen bonds with water molecules. These strong intermolecular interactions overcome any polarity differences, making ethanol miscible with water in all proportions.
340. Which molecule exhibits the weakest hydrogen bonding among H₂O, HF, and NH₃?
ⓐ. H₂O
ⓑ. HF
ⓒ. NH₃
ⓓ. All have equal strength
Correct Answer: NH₃
Explanation: Although NH₃ has three hydrogens, nitrogen is less electronegative than oxygen and fluorine, and it has only one lone pair. This limits hydrogen bonding ability. In contrast, HF has the strongest H-bonds per bond, and H₂O forms the most extensive network of hydrogen bonds.
341. Why does water have an unusually high boiling point compared to H₂S?
ⓐ. Because water has greater molecular mass
ⓑ. Because water molecules form extensive intermolecular hydrogen bonding
ⓒ. Because H₂S is non-polar
ⓓ. Because oxygen atoms repel each other strongly
Correct Answer: Because water molecules form extensive intermolecular hydrogen bonding
Explanation: In H₂O, each molecule can form up to four hydrogen bonds, creating a strong intermolecular network. Breaking these bonds requires significant energy, leading to an abnormally high boiling point. H₂S does not form hydrogen bonds due to low electronegativity of sulfur, so it has a much lower boiling point.
342. Why does ice float on water?
ⓐ. Because ice is lighter than water due to absence of hydrogen bonds
ⓑ. Because hydrogen bonding forces ice into an open hexagonal lattice, making it less dense than liquid water
ⓒ. Because water molecules are larger in liquid state
ⓓ. Because liquid water contains ionic bonds
Correct Answer: Because hydrogen bonding forces ice into an open hexagonal lattice, making it less dense than liquid water
Explanation: In solid ice, each water molecule forms four hydrogen bonds, creating a rigid open lattice with empty spaces. This makes ice less dense than water, where bonds are partially broken and molecules are more closely packed.
343. Which of the following is a direct chemical consequence of hydrogen bonding?
ⓐ. Greater tendency of salts to dissociate in water
ⓑ. Unusually low solubility of alcohols
ⓒ. Abnormally high volatility of o-nitrophenol compared to p-nitrophenol
ⓓ. Reduction in covalent character of bonds
Correct Answer: Abnormally high volatility of o-nitrophenol compared to p-nitrophenol
Explanation: o-Nitrophenol has intramolecular hydrogen bonding, reducing intermolecular attraction between molecules. This makes it more volatile and gives it a lower boiling point compared to p-nitrophenol, where intermolecular hydrogen bonding raises boiling point.
344. Which property of liquid water is explained by hydrogen bonding?
ⓐ. Low specific heat
ⓑ. High viscosity and high surface tension
ⓒ. Absence of polarity
ⓓ. Complete lack of solubility
Correct Answer: High viscosity and high surface tension
Explanation: Extensive intermolecular hydrogen bonding in water molecules creates strong cohesive forces. These increase resistance to flow (viscosity) and pull surface molecules inward, producing high surface tension.
345. Why do HF molecules form zig-zag chains in the solid state?
ⓐ. Because HF molecules are nonpolar
ⓑ. Because hydrogen bonds link HF molecules into chains
ⓒ. Because fluorine cannot form covalent bonds
ⓓ. Because HF is ionic in nature
Correct Answer: Because hydrogen bonds link HF molecules into chains
Explanation: In solid HF, each molecule forms hydrogen bonds with neighboring molecules, creating zig-zag chains. This explains its high melting and boiling points relative to other hydrogen halides.
346. Which of the following compounds is more soluble in water due to hydrogen bonding?
ⓐ. Benzene
ⓑ. Ethanol
ⓒ. Carbon tetrachloride
ⓓ. Methane
Correct Answer: Ethanol
Explanation: Ethanol contains an –OH group capable of forming hydrogen bonds with water molecules. This makes ethanol miscible with water in all proportions. Nonpolar compounds like benzene and methane cannot form hydrogen bonds and are insoluble in water.
347. Why does glycerol (C₃H₅(OH)₃) have a high boiling point and viscosity?
ⓐ. Because of its large molecular mass
ⓑ. Because each molecule forms multiple intermolecular hydrogen bonds
ⓒ. Because glycerol molecules are nonpolar
ⓓ. Because glycerol contains ionic bonds
Correct Answer: Because each molecule forms multiple intermolecular hydrogen bonds
Explanation: Glycerol has three hydroxyl groups per molecule, each capable of forming hydrogen bonds. This results in strong intermolecular forces, giving glycerol high viscosity, high boiling point, and strong water solubility.
348. Which of the following explains the higher boiling point of NH₃ compared to PH₃?
ⓐ. NH₃ is lighter than PH₃
ⓑ. NH₃ forms hydrogen bonds, while PH₃ does not
ⓒ. NH₃ has ionic bonds, while PH₃ has covalent bonds
ⓓ. NH₃ is nonpolar, while PH₃ is polar
Correct Answer: NH₃ forms hydrogen bonds, while PH₃ does not
Explanation: NH₃ molecules form intermolecular hydrogen bonds via N–H···N interactions. PH₃ lacks hydrogen bonding because phosphorus is much less electronegative. This explains why NH₃ has a significantly higher boiling point than PH₃ despite its lower molar mass.
349. Which statement explains why proteins and DNA depend on hydrogen bonding for their structure?
ⓐ. Hydrogen bonding stabilizes α-helices, β-sheets, and base pairings
ⓑ. Proteins and DNA are nonpolar molecules
ⓒ. Hydrogen bonding makes them soluble in hydrocarbons
ⓓ. Hydrogen bonding reduces their polarity
Correct Answer: Hydrogen bonding stabilizes α-helices, β-sheets, and base pairings
Explanation: In proteins, N–H···O hydrogen bonds stabilize secondary structures like α-helices and β-sheets. In DNA, hydrogen bonds between base pairs (A–T with 2 bonds, G–C with 3 bonds) stabilize the double helix while allowing strand separation during replication.
350. Which compound is less soluble in water due to intramolecular hydrogen bonding?
ⓐ. o-nitrophenol
ⓑ. p-nitrophenol
ⓒ. Ethanol
ⓓ. Ammonia
Correct Answer: o-nitrophenol
Explanation: In o-nitrophenol, the hydroxyl group forms a hydrogen bond with the ortho-nitro group within the same molecule (intramolecular bonding). This reduces its ability to hydrogen bond with water molecules, lowering solubility compared to p-nitrophenol, which forms intermolecular hydrogen bonds.
351. Which of the following molecules cannot be explained satisfactorily by Valence Bond Theory but is explained by Molecular Orbital Theory?
ⓐ. N₂
ⓑ. O₂
ⓒ. HCl
ⓓ. HF
Correct Answer: O₂
Explanation: Valence Bond Theory predicts O₂ to be diamagnetic, but experimental evidence shows O₂ is paramagnetic. MOT explains this by placing two unpaired electrons in the degenerate π*2px and π*2py orbitals, giving O₂ bond order 2 and paramagnetic character.
352. What is the bond order of the superoxide ion, O₂⁻, according to Molecular Orbital Theory?
ⓐ. 1
ⓑ. 1.5
ⓒ. 2
ⓓ. 2.5
Correct Answer: 1.5
Explanation: O₂⁻ has 17 electrons. MO filling: σ1s² σ*1s² σ2s² σ*2s² σ2pz² π2px² π2py² π*2px² π*2py¹. Bond order = (10 – 7)/2 = 1.5. This explains why O₂⁻ is less stable and has longer bond length than O₂.
353. Which of the following species is diamagnetic according to MO theory?
ⓐ. B₂
ⓑ. O₂
ⓒ. C₂
ⓓ. O₂⁻
Correct Answer: C₂
Explanation: C₂ has 12 electrons. MO filling: σ1s² σ*1s² σ2s² σ*2s² π2px² π2py². All electrons are paired, so C₂ is diamagnetic. In contrast, B₂ and O₂ have unpaired electrons.
354. Which of the following shows sp³d² hybridization with square planar geometry?
ⓐ. XeF₄
ⓑ. SF₆
ⓒ. PCl₅
ⓓ. IF₇
Correct Answer: XeF₄
Explanation: XeF₄ has 6 regions of electron density (4 bonding pairs, 2 lone pairs). This corresponds to sp³d² hybridization. Due to lone pair–lone pair repulsion, the molecular shape becomes square planar, not octahedral.
355. In acetylene (C₂H₂), each carbon atom undergoes:
ⓐ. sp hybridization
ⓑ. sp² hybridization
ⓒ. sp³ hybridization
ⓓ. sp³d hybridization
Correct Answer: sp hybridization
Explanation: In C₂H₂, carbon uses sp hybrid orbitals to form sigma bonds with hydrogen and each other, while the unhybridized 2p orbitals overlap sideways to form two π bonds. This gives a triple bond between carbons (1 σ + 2 π).
356. The bond angle in NH₄⁺ ion is:
ⓐ. 90°
ⓑ. 107°
ⓒ. 109.5°
ⓓ. 120°
Correct Answer: 109.5°
Explanation: NH₄⁺ has 4 bonding pairs and no lone pairs, leading to perfect sp³ hybridization with a tetrahedral geometry and bond angles of 109.5°.
357. Which of the following molecules has both sigma and pi bonds but no lone pairs on the central atom?
ⓐ. H₂O
ⓑ. CO₂
ⓒ. NH₃
ⓓ. XeF₂
Correct Answer: CO₂
Explanation: In CO₂, carbon is sp hybridized and forms two double bonds (C=O). Each double bond consists of one σ bond and one π bond. Carbon has no lone pairs, and the molecule is linear.
358. Which of the following statements about bond order is correct?
ⓐ. Higher bond order means weaker bonds and longer bond length
ⓑ. Higher bond order means stronger bonds and shorter bond length
ⓒ. Bond order has no relation with bond length
ⓓ. Bond order applies only to covalent bonds, not ionic bonds
Correct Answer: Higher bond order means stronger bonds and shorter bond length
Explanation: Bond order directly correlates with bond strength and inversely with bond length. For example, N₂ (bond order 3) has a stronger, shorter bond than O₂ (bond order 2).
359. What is the hybridization of the central atom in XeF₂, and what is its molecular shape?
ⓐ. sp³, trigonal pyramidal
ⓑ. sp³d, linear
ⓒ. sp³d², octahedral
ⓓ. sp³d³, pentagonal bipyramidal
Correct Answer: sp³d, linear
Explanation: XeF₂ has 5 electron domains (2 bonding, 3 lone pairs). With sp³d hybridization, the lone pairs occupy equatorial positions, leaving the fluorine atoms at axial positions, giving a linear geometry.
360. Which of the following species has the shortest bond length?
ⓐ. O₂
ⓑ. O₂⁺
ⓒ. O₂⁻
ⓓ. O₂²⁻
Correct Answer: O₂⁺
Explanation: Bond order comparison: O₂⁺ = 2.5, O₂ = 2, O₂⁻ = 1.5, O₂²⁻ = 1. Higher bond order corresponds to stronger bonds and shorter bond length. Thus, O₂⁺ has the shortest bond length.
361. Which of the following correctly represents the formation of ammonium ion (NH₄⁺)?
ⓐ. $NH₃ + H^+ \rightarrow NH₄^+$
ⓑ. $NH₃ + H_2 \rightarrow NH₄^+$
ⓒ. $NH₃ \rightarrow NH₄^+ + e^-$
ⓓ. $N_2 + 3H_2 \rightarrow 2NH₄^+$
Correct Answer: $NH₃ + H^+ \rightarrow NH₄^+$
Explanation: NH₃ donates a lone pair on nitrogen to H⁺, forming a coordinate covalent bond. This produces the ammonium ion, NH₄⁺. Options B and D are chemically incorrect, while C would imply oxidation, which is not the case here.
362. Which reaction represents the lattice enthalpy of NaCl?
ⓐ. $Na^+ (aq) + Cl^- (aq) \rightarrow NaCl (s)$
ⓑ. $Na (s) + \tfrac{1}{2}Cl_2 (g) \rightarrow NaCl (s)$
ⓒ. $Na^+ (g) + Cl^- (g) \rightarrow NaCl (s)$
ⓓ. $NaCl (s) \rightarrow Na^+ (g) + Cl^- (g)$
Correct Answer: $Na^+ (g) + Cl^- (g) \rightarrow NaCl (s)$
Explanation: Lattice enthalpy is defined as the energy released when gaseous ions combine to form one mole of crystalline solid. Option D represents the reverse (lattice dissociation).
363. Which equation shows the formation of O₂ molecule according to Molecular Orbital Theory?
ⓐ. $O + O \rightarrow O_2$
ⓑ. $2O(g) \rightarrow O_2(g)$ with filling of orbitals: σ1s² σ*1s² σ2s² σ*2s² σ2pz² π2px² π2py² π*2px¹ π*2py¹
ⓒ. $O^{2-} + O^{2+} \rightarrow O_2$
ⓓ. $O_2 \rightarrow 2O$
Correct Answer: $2O(g) \rightarrow O_2(g)$ with filling of orbitals: σ1s² σ*1s² σ2s² σ*2s² σ2pz² π2px² π2py² π*2px¹ π*2py¹
Explanation: Molecular orbital theory explains O₂ formation with 16 total electrons. The MO configuration reveals two unpaired electrons in π\* orbitals, explaining its paramagnetism.
364. Which of the following chemical equations shows intramolecular hydrogen bonding?
ⓐ. $o\text{-nitrophenol} \, (OH···O=NO)$
ⓑ. $p\text{-nitrophenol} + H_2O \rightarrow H\text{-bonded complex}$
ⓒ. $HCl + NH_3 \rightarrow NH_4Cl$
ⓓ. $Na^+ + Cl^- \rightarrow NaCl$
Correct Answer: $o\text{-nitrophenol} \, (OH···O=NO)$
Explanation: In ortho-nitrophenol, hydrogen of the –OH group bonds with oxygen of –NO₂ within the same molecule. This intramolecular H-bond lowers solubility and boiling point compared to the para-isomer.
365. Which equation corresponds to the formation of a π bond in ethene (C₂H₄)?
ⓐ. $sp^2–sp^2$ overlap of carbon orbitals + sideways overlap of p orbitals → C=C
ⓑ. $sp–sp$ overlap of carbon orbitals → C≡C
ⓒ. $sp^3–sp^3$ overlap of carbon orbitals → C–C single bond
ⓓ. $s–s$ overlap only → C–C bond
Correct Answer: $sp^2–sp^2$ overlap of carbon orbitals + sideways overlap of p orbitals → C=C
Explanation: In ethene, each carbon atom is sp² hybridized. One σ bond is formed by head-on sp²–sp² overlap, and one π bond is formed by sideways overlap of unhybridized p orbitals, producing a double bond.
366. Which chemical equation represents the formation of BeCl₂ molecule?
ⓐ. $Be (1s^2 2s^2) \rightarrow Be^+ + e^-$
ⓑ. $Be (2s^2) \rightarrow sp \, hybridization \rightarrow sp$ orbitals overlap with 3p orbitals of Cl
ⓒ. $Be (g) + Cl (g) \rightarrow BeCl_2 (s)$ without hybridization
ⓓ. $Be^{2+} + 2Cl^- \rightarrow BeCl_2$ (ionic only)
Correct Answer: $Be (2s^2) \rightarrow sp \, hybridization \rightarrow sp$ orbitals overlap with 3p orbitals of Cl
Explanation: In BeCl₂, beryllium undergoes sp hybridization, giving linear geometry. The sp orbitals overlap with p orbitals of chlorine to form σ bonds. This covalent bonding explains its molecular structure.
367. Which chemical equation represents the concept of bond dissociation enthalpy?
ⓐ. $H_2 (g) \rightarrow 2H (g)$
ⓑ. $2H (g) \rightarrow H_2 (g)$
ⓒ. $H_2 (g) + Cl_2 (g) \rightarrow 2HCl (g)$
ⓓ. $Na (s) + Cl_2 (g) \rightarrow NaCl (s)$
Correct Answer: $H_2 (g) \rightarrow 2H (g)$
Explanation: Bond dissociation enthalpy is defined as the energy required to break one mole of covalent bonds in the gaseous state. For hydrogen, it corresponds to breaking H–H bond in H₂(g).
368. Which equation shows the hydrogen bonding responsible for dimer formation of carboxylic acids?
ⓐ. $2R–COOH \, \rightleftharpoons \, R–COOH···HOOC–R$
ⓑ. $R–COOH \rightarrow R–COO^- + H^+$
ⓒ. $R–COOH + NaOH \rightarrow R–COONa + H_2O$
ⓓ. $R–COOH \rightarrow R–C≡O$
Correct Answer: $2R–COOH \, \rightleftharpoons \, R–COOH···HOOC–R$
Explanation: Carboxylic acids dimerize in vapor phase and non-polar solvents due to strong intermolecular hydrogen bonding between the –OH and C=O groups. This explains their abnormally high boiling points.
369. Which chemical equation correctly represents the formation of XeF₂?
ⓐ. $Xe + 2F_2 \rightarrow XeF_4$
ⓑ. $Xe + F_2 \rightarrow XeF_2$ under high pressure and heat
ⓒ. $Xe^{2+} + 2F^- \rightarrow XeF_2$
ⓓ. $Xe + 3F_2 \rightarrow XeF_6$
Correct Answer: $Xe + F_2 \rightarrow XeF_2$ under high pressure and heat
Explanation: XeF₂ is prepared by heating xenon and fluorine in a 1:1 ratio at \~400°C under high pressure. Xe undergoes sp³d hybridization, giving a linear shape due to three equatorial lone pairs.
370. Which equation shows the disproportionation of hydrogen peroxide involving hydrogen bonding?
ⓐ. $2H_2O_2 \rightarrow 2H_2O + O_2$
ⓑ. $H_2O_2 \rightarrow H_2 + O_2$
ⓒ. $2H_2O_2 \rightarrow H_2O + 2O_2$
ⓓ. $H_2O_2 + H_2O \rightarrow H_3O^+ + OH^-$
Correct Answer: $2H_2O_2 \rightarrow 2H_2O + O_2$
Explanation: Hydrogen peroxide decomposes to water and oxygen. Strong intermolecular hydrogen bonding between H₂O₂ molecules stabilizes the liquid but also makes it unstable thermodynamically, leading to disproportionation on heating or catalysis.
371. Which chemical equation represents the formation of ozone (O₃) from dioxygen?
ⓐ. $O_2 (g) \rightarrow O_3 (g)$
ⓑ. $O_2 (g) + O (g) \rightarrow O_3 (g)$
ⓒ. $3O (g) \rightarrow O_3 (g)$
ⓓ. $O_3 (g) \rightarrow O_2 (g) + O (g)$
Correct Answer: $O_2 (g) + O (g) \rightarrow O_3 (g)$
Explanation: Ozone is formed when a dioxygen molecule reacts with an oxygen atom in the atmosphere. In the resonance hybrid, O₃ exhibits delocalized bonding with bond order 1.5, shorter than a single bond but longer than a double bond.
372. Which of the following correctly shows the bond formation in CO molecule?
ⓐ. $C (2s^2 2p^2) + O (2s^2 2p^4) \rightarrow CO$ with one σ bond only
ⓑ. CO contains one σ bond and one π bond only
ⓒ. CO contains one σ bond, two π bonds, and one coordinate bond from O to C
ⓓ. CO contains purely ionic bonding between C²⁺ and O²⁻
Correct Answer: CO contains one σ bond, two π bonds, and one coordinate bond from O to C
Explanation: CO has a triple bond character (1 σ + 2 π) and an additional coordinate bond from oxygen’s lone pair to carbon. This explains its strong bond enthalpy and dipole moment, despite carbon being less electronegative.
373. Which chemical equation represents the resonance stabilization in benzene?
ⓐ. $C_6H_6 \rightarrow C_6H_6$ with alternating single and double bonds fixed
ⓑ. $C_6H_6 \leftrightarrow$ resonance structures with alternating single and double bonds
ⓒ. $3C_2H_2 \rightarrow C_6H_6$
ⓓ. $C_6H_6 \rightarrow C_6H_{12}$
Correct Answer: $C_6H_6 \leftrightarrow$ resonance structures with alternating single and double bonds
Explanation: Benzene is stabilized by delocalization of π electrons over the six carbons. Resonance produces equivalent Kekulé structures, and the true structure is a hybrid with equal C–C bond lengths (bond order \~1.5).
374. Which equation represents the concept of bond enthalpy in chlorine?
ⓐ. $Cl_2 (g) \rightarrow 2Cl (g)$
ⓑ. $Cl^- (aq) \rightarrow Cl (g) + e^-$
ⓒ. $HCl (g) \rightarrow H (g) + Cl (g)$
ⓓ. $NaCl (s) \rightarrow Na^+ (g) + Cl^- (g)$
Correct Answer: $Cl_2 (g) \rightarrow 2Cl (g)$
Explanation: Bond enthalpy is the energy required to break one mole of covalent bonds in the gaseous state. For Cl₂, it is the dissociation into two chlorine atoms. This explains chlorine’s reactivity in halogenation reactions.
375. Which of the following reactions shows the concept of coordinate covalent bond formation?
ⓐ. $H^+ + H_2O \rightarrow H_3O^+$
ⓑ. $Na^+ + Cl^- \rightarrow NaCl$
ⓒ. $H_2 + Cl_2 \rightarrow 2HCl$
ⓓ. $2K + Cl_2 \rightarrow 2KCl$
Correct Answer: $H^+ + H_2O \rightarrow H_3O^+$
Explanation: The hydronium ion is formed when water donates a lone pair of electrons to H⁺. This bond is coordinate covalent because both electrons in the bond originate from the oxygen atom.
376. Which chemical equation illustrates back bonding in BF₃?
ⓐ. $BF_3 \rightarrow sp^2$ hybridization, planar trigonal
ⓑ. $F : \rightarrow B$ (back donation of electrons from fluorine’s filled p orbital to boron’s empty p orbital)
ⓒ. $B (g) + 3F (g) \rightarrow BF_3 (g)$
ⓓ. $BF_3 + NH_3 \rightarrow F_3B \cdot NH_3$
Correct Answer: $F : \rightarrow B$ (back donation of electrons from fluorine’s filled p orbital to boron’s empty p orbital)
Explanation: In BF₃, boron is electron-deficient. Back bonding occurs when fluorine donates lone pair electrons into the empty p orbital of boron. This gives BF₃ partial double bond character and shortens the B–F bond length.
377. Which of the following equations represents the hydration of Na⁺ ions in aqueous solution?
ⓐ. $Na^+ (aq) \rightarrow Na^+ (g)$
ⓑ. $Na^+ (g) + H_2O (l) \rightarrow [Na(H_2O)_n]^+$
ⓒ. $Na (s) \rightarrow Na^+ (aq) + e^-$
ⓓ. $Na^+ (g) + Cl^- (g) \rightarrow NaCl (s)$
Correct Answer: $Na^+ (g) + H_2O (l) \rightarrow [Na(H_2O)_n]^+$
Explanation: Hydration involves ion–dipole interactions between Na⁺ and polar water molecules. Water molecules orient with their oxygen atoms toward Na⁺, forming a hydration shell, which stabilizes ions in solution.
378. Which of the following is the correct Lewis representation of SO₄²⁻ ion?
ⓐ. One double bond with S=O and three single bonds with S–O⁻
ⓑ. Four single bonds with negative charges delocalized
ⓒ. Two double bonds with two S=O and two S–O⁻
ⓓ. Resonance hybrid with equivalent S–O bonds and delocalized negative charge
Correct Answer: Resonance hybrid with equivalent S–O bonds and delocalized negative charge
Explanation: The true structure of sulfate ion is a resonance hybrid with four equivalent S–O bonds. The two negative charges are delocalized over the oxygen atoms, giving each bond partial double bond character.
379. Which chemical equation represents the preparation of PCl₅, an sp³d hybridized molecule?
ⓐ. $PCl_3 + Cl_2 \rightarrow PCl_5$
ⓑ. $P + Cl_2 \rightarrow PCl_3$
ⓒ. $P + 2Cl_2 \rightarrow PCl_4$
ⓓ. $PCl_5 \rightarrow PCl_3 + Cl_2$
Correct Answer: $PCl_3 + Cl_2 \rightarrow PCl_5$
Explanation: PCl₅ is formed by chlorination of PCl₃. Phosphorus undergoes sp³d hybridization, giving a trigonal bipyramidal geometry with two axial and three equatorial bonds.
380. Which equation represents the reaction of hydrogen bonding in ammonia?
ⓐ. $NH_3 + H_2O \rightarrow NH_4^+ + OH^-$
ⓑ. $NH_3···NH_3$ (H–bonding between H of one NH₃ and lone pair of another)
ⓒ. $NH_3 \rightarrow N^{3-} + 3H^+$
ⓓ. $NH_3 + Cl_2 \rightarrow NCl_3 + HCl$
Correct Answer: $NH_3···NH_3$ (H–bonding between H of one NH₃ and lone pair of another)
Explanation: In liquid or solid ammonia, intermolecular hydrogen bonding occurs between the partially positive hydrogen of one molecule and the lone pair of another nitrogen. This explains its higher boiling point compared to PH₃, which cannot form H-bonds.
381. Which of the following chemical equations represents the dimerization of NO₂?
ⓐ. $NO_2 \rightarrow N_2 + O_2$
ⓑ. $2NO_2 \rightarrow N_2O_4$
ⓒ. $NO_2 \rightarrow NO + O$
ⓓ. $N_2O_4 \rightarrow 2NO$
Correct Answer: $2NO_2 \rightarrow N_2O_4$
Explanation: Nitrogen dioxide has an unpaired electron and is paramagnetic. Two NO₂ molecules combine via intermolecular interactions (N–O–N bridge) to form dinitrogen tetroxide (N₂O₄), which is diamagnetic. This is a classic example of equilibrium between a monomer and a dimer influenced by temperature.
382. Which of the following correctly represents the disproportionation of chlorine in water?
ⓐ. $Cl_2 + H_2O \rightarrow HCl$
ⓑ. $Cl_2 + H_2O \rightarrow HCl + HClO$
ⓒ. $2Cl_2 + 2H_2O \rightarrow 4HCl$
ⓓ. $Cl_2 + H_2O \rightarrow ClO_3^- + Cl^-$
Correct Answer: $Cl_2 + H_2O \rightarrow HCl + HClO$
Explanation: In water, chlorine undergoes disproportionation. One atom is reduced to –1 in HCl, and the other is oxidized to +1 in HClO. This explains chlorine’s bleaching and disinfecting properties.
383. Which equation correctly represents the hybridization in SF₆?
ⓐ. $S (3s^2 3p^4) \rightarrow sp^3$ → octahedral
ⓑ. $S (3s^2 3p^4) \rightarrow sp^3d^2$ → octahedral
ⓒ. $S (3s^2 3p^4) \rightarrow sp^3d$ → trigonal bipyramidal
ⓓ. $S (3s^2 3p^4) \rightarrow sp^2$ → trigonal planar
Correct Answer: $S (3s^2 3p^4) \rightarrow sp^3d^2$ → octahedral
Explanation: In SF₆, sulfur uses one 3s, three 3p, and two 3d orbitals to form six sp³d² hybrid orbitals. These arrange octahedrally with 90° bond angles, consistent with experimental geometry.
384. Which chemical equation corresponds to the hydrolysis of PCl₅?
ⓐ. $PCl_5 + H_2O \rightarrow POCl_3 + 2HCl$
ⓑ. $PCl_5 + 4H_2O \rightarrow H_3PO_4 + 5HCl$
ⓒ. Both A and B depending on amount of water
ⓓ. $PCl_5 + H_2O \rightarrow PCl_3 + Cl_2$
Correct Answer: Both A and B depending on amount of water
Explanation: With limited water, PCl₅ hydrolyzes to phosphoryl chloride (POCl₃). With excess water, complete hydrolysis produces orthophosphoric acid (H₃PO₄). These reactions highlight PCl₅’s sp³d hybridization and reactivity.
385. Which reaction represents the formation of the peroxide ion?
ⓐ. $O_2 + 2e^- \rightarrow O_2^{2-}$
ⓑ. $O_2 + e^- \rightarrow O_2^-$
ⓒ. $O_2^{2-} \rightarrow O_2 + 2e^-$
ⓓ. $2O^{2-} \rightarrow O_2^{2-}$
Correct Answer: $O_2 + 2e^- \rightarrow O_2^{2-}$
Explanation: The peroxide ion is formed by addition of two electrons to dioxygen. In MO terms, O₂²⁻ has 18 electrons with bond order = (10 – 8)/2 = 1, consistent with its weaker O–O bond compared to O₂.
386. Which of the following correctly explains the bleaching property of ozone?
ⓐ. $O_3 \rightarrow O_2 + [O]$
ⓑ. $O_3 + H_2O \rightarrow H_2O_2 + O_2$
ⓒ. $O_3 \rightarrow 3O$
ⓓ. $O_3 + Cl_2 \rightarrow ClO_2 + O_2$
Correct Answer: $O_3 \rightarrow O_2 + [O]$
Explanation: Ozone decomposes to molecular oxygen and nascent oxygen \[O], a powerful oxidizing agent. The nascent oxygen bleaches by oxidizing colored compounds into colorless products.
387. Which of the following shows the resonance structures of carbonate ion?
ⓐ. $CO_3^{2-} \rightarrow$ one C=O double bond and two C–O single bonds fixed
ⓑ. $CO_3^{2-} \leftrightarrow$ three equivalent structures with delocalized π bonds
ⓒ. $CO_3^{2-} \rightarrow$ one double bond only
ⓓ. $CO_3^{2-} \rightarrow$ purely ionic between C⁴⁺ and O²⁻
Correct Answer: $CO_3^{2-} \leftrightarrow$ three equivalent structures with delocalized π bonds
Explanation: The carbonate ion is stabilized by resonance. Negative charge and π electrons are delocalized equally across the three oxygen atoms, giving all C–O bonds equal length (bond order = 1⅓).
388. Which chemical equation shows the decomposition of hydrogen peroxide catalyzed by MnO₂?
ⓐ. $2H_2O_2 \rightarrow 2H_2O + O_2$
ⓑ. $H_2O_2 \rightarrow H_2 + O_2$
ⓒ. $H_2O_2 + H_2O \rightarrow H_3O^+ + OH^-$
ⓓ. $H_2O_2 + 2MnO_2 \rightarrow 2MnO + O_2$
Correct Answer: $2H_2O_2 \rightarrow 2H_2O + O_2$
Explanation: Hydrogen peroxide is unstable and decomposes into water and oxygen. MnO₂ acts as a catalyst, lowering activation energy. This reaction is accelerated by heat and explains why H₂O₂ is stored with stabilizers.
389. Which hybridization and geometry are shown in XeF₄?
ⓐ. sp³d², square planar
ⓑ. sp³, tetrahedral
ⓒ. sp³d, trigonal bipyramidal
ⓓ. sp³d³, pentagonal bipyramidal
Correct Answer: sp³d², square planar
Explanation: In XeF₄, xenon has 6 electron pairs (4 bonding, 2 lone). With sp³d² hybridization, electron geometry is octahedral, but two lone pairs occupy opposite positions, leaving a square planar molecular shape.
390. Which of the following chemical equations shows the amphoteric nature of Al₂O₃?
ⓐ. $Al_2O_3 + 6HCl \rightarrow 2AlCl_3 + 3H_2O$
ⓑ. $Al_2O_3 + 2NaOH + 3H_2O \rightarrow 2Na[Al(OH)_4]$
ⓒ. Both A and B
ⓓ. $Al_2O_3 + H_2 \rightarrow Al + H_2O$
Correct Answer: Both A and B
Explanation: Al₂O₃ reacts with acids (like HCl) showing basic behavior, and with bases (like NaOH) showing acidic behavior. This dual reactivity confirms its amphoteric nature.
391. Which reaction correctly represents the preparation of XeF₆?
ⓐ. $Xe + 3F_2 \xrightarrow{573K,\,60atm} XeF_6$
ⓑ. $Xe + F_2 \rightarrow XeF_2$
ⓒ. $Xe + 2F_2 \rightarrow XeF_4$
ⓓ. $XeF_6 \rightarrow Xe + 3F_2$
Correct Answer: $Xe + 3F_2 \xrightarrow{573K,\,60atm} XeF_6$
Explanation: XeF₆ is formed by heating xenon with excess fluorine at high temperature and pressure. Xe undergoes sp³d³ hybridization, giving a distorted octahedral geometry due to lone pair repulsion.
392. Which chemical equation represents the bond dissociation enthalpy of oxygen?
ⓐ. $O_2 (g) \rightarrow 2O (g)$
ⓑ. $O_2 (g) + 2e^- \rightarrow 2O^{2-}$
ⓒ. $2O (g) \rightarrow O_2 (g)$
ⓓ. $O_2 \rightarrow O_2^+ + e^-$
Correct Answer: $O_2 (g) \rightarrow 2O (g)$
Explanation: Bond dissociation enthalpy is the energy required to break one mole of covalent bonds in the gaseous state. For O₂, it is the energy to break the double bond into two oxygen atoms.
393. Which equation shows the formation of ammonium chloride through acid–base reaction?
ⓐ. $NH_3 + HCl \rightarrow NH_4Cl$
ⓑ. $NH_3 + Cl_2 \rightarrow NCl_3 + HCl$
ⓒ. $NH_3 \rightarrow NH_2^- + H^+$
ⓓ. $NH_3 + Na \rightarrow NaNH_2 + H_2$
Correct Answer: $NH_3 + HCl \rightarrow NH_4Cl$
Explanation: Ammonia acts as a base and donates its lone pair to H⁺ from HCl, forming NH₄⁺. This then combines with Cl⁻ to produce ammonium chloride, an ionic salt with strong lattice energy.
394. Which of the following correctly represents the hydrolysis of XeF₄?
ⓐ. $XeF_4 + 2H_2O \rightarrow XeO_2F_2 + 4HF$
ⓑ. $XeF_4 + H_2O \rightarrow XeO_3 + HF$
ⓒ. $XeF_4 + O_2 \rightarrow XeO_4 + F_2$
ⓓ. $XeF_4 + NaOH \rightarrow Xe + NaF$
Correct Answer: $XeF_4 + 2H_2O \rightarrow XeO_2F_2 + 4HF$
Explanation: Hydrolysis of XeF₄ produces xenon oxyfluoride (XeO₂F₂) along with HF. Further hydrolysis in excess water can yield XeO₃. This reaction shows xenon’s ability to form stable oxyfluorides.
395. Which reaction illustrates the hydrogen bonding in carboxylic acids?
ⓐ. $2R–COOH \leftrightarrow R–COOH···HOOC–R$
ⓑ. $R–COOH + NaOH \rightarrow R–COONa + H_2O$
ⓒ. $R–COOH \rightarrow R–C≡O + H_2$
ⓓ. $R–COOH + HCl \rightarrow R–COCl + H_2O$
Correct Answer: $2R–COOH \leftrightarrow R–COOH···HOOC–R$
Explanation: Carboxylic acids form dimers in vapor phase and nonpolar solvents due to intermolecular hydrogen bonding between –OH and C=O groups. This accounts for their unusually high boiling points compared to other compounds of similar molecular mass.
This is the final part of Class 11 Chemistry MCQs – Chapter 4: Chemical Bonding and Molecular Structure (Part 4). The full chapter offers 395 MCQs with correct answers and explanations, divided into 4 well-structured parts for better practice. Based on the NCERT/CBSE syllabus, these MCQs are highly recommended for board exams and competitive exams like JEE, NEET, AIIMS, and state-level entrance tests. In this closing part, you will solve the remaining 95 multiple-choice questions covering topics like Hydrogen bonding (intermolecular and intramolecular), examples (H2O, NH3, HF), and its consequences on physical & chemical properties. Completing this set will ensure that you have thoroughly revised the entire chapter and are exam-ready.
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