रसायन विज्ञान (Chemistry) – Chemistry MCQ
रसायन विज्ञान (Chemistry) – इन्जिनियरिङ प्रवेश
Chemistry · Engineering Entrance – Mathematics, Physics, Chemistry & English · ७२८ प्रश्न
७२८ प्रश्न उपलब्ध। मोड छान्नुहोस्:
रसायन विज्ञान (Chemistry): प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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Water (H₂O) has a much higher boiling point than hydrogen sulphide (H₂S) mainly because of:
सही उत्तर: घ) Hydrogen bonding in water
Strong intermolecular hydrogen bonds between H₂O molecules need extra energy to break. H₂O actually has a lower molar mass (18) than H₂S (34), so mass cannot explain it.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The hybridisation and shape of BF₃ are:
सही उत्तर: ग) sp², trigonal planar
Boron forms three bonds with no lone pair, using sp² hybrids at 120° in a plane. Trigonal pyramidal shapes (like NH₃) need a lone pair on the central atom.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which molecule has zero dipole moment?
सही उत्तर: ख) CO₂
CO₂ is linear, so the two equal C=O bond dipoles cancel. SO₂ is bent, so its bond dipoles do not cancel.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The bond order of the superoxide ion (O₂⁻) is:
सही उत्तर: क) 1.5
O₂ has bond order 2; adding one electron to an antibonding π* orbital lowers it by ½ to 1.5. A bond order of 1 belongs to the peroxide ion O₂²⁻.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to molecular orbital theory, the bond order of N₂ is:
सही उत्तर: ग) 3
N₂ has 8 bonding and 2 antibonding valence electrons in MO terms (10 and 4 if the 1s electrons are included); bond order = (8 − 2)/2 = 3, a triple bond. Bond order 2 belongs to O₂.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The shape of the PCl₅ molecule in the gas phase is:
सही उत्तर: ख) Trigonal bipyramidal
P in PCl₅ is sp³d hybridised with five bond pairs and no lone pair, giving a trigonal bipyramidal shape. Square pyramidal shapes occur with five bond pairs plus one lone pair, as in BrF₅.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The shape of the XeF₄ molecule is:
सही उत्तर: क) Square planar
Xe in XeF₄ has four bond pairs and two lone pairs (sp³d²); the lone pairs sit opposite each other, leaving a square planar shape. The electron-pair geometry is octahedral, not the molecular shape.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The hybridisation of sulphur in SF₆ is:
सही उत्तर: घ) sp³d²
Sulphur forms six S–F bonds using six sp³d² hybrid orbitals, giving an octahedral shape. sp³d gives five hybrid orbitals (trigonal bipyramidal, as in PCl₅).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Zirconium (Zr) and hafnium (Hf) have almost identical atomic radii because of:
सही उत्तर: क) Lanthanoid contraction
The poor shielding by 4f electrons in the lanthanoids reduces the size of Hf so it nearly equals Zr. The inert pair effect concerns the reluctance of ns² electrons to bond in heavy p-block elements.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Among the isoelectronic ions N³⁻, O²⁻, F⁻ and Na⁺, the smallest is:
सही उत्तर: घ) Na⁺
All four have 10 electrons; Na⁺ has the highest nuclear charge (11 protons), so it pulls the electrons in most strongly. N³⁻, with only 7 protons, is the largest.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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