चिकित्सा शिक्षा आयोग (CEE) बीडीएस प्रवेश परीक्षा तयारी
चिकित्सा शिक्षा आयोग (CEE) – बीडीएस प्रवेश परीक्षा
CEE – BDS Entrance · Medical Education Commission – CEE
२,०३९ प्रश्न उपलब्ध। मोड छान्नुहोस्:
MBBS/BDS/Nursing प्रवेश: 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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The number of σ (sigma) bonds in an ethene (C₂H₄) molecule is:
सही उत्तर: क) 5
Ethene has four C–H σ bonds and one C–C σ bond (the double bond is one σ + one π), giving 5 σ bonds. Counting the double bond as two σ bonds wrongly gives 6.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Water has a much higher boiling point than H₂S mainly because of:
सही उत्तर: घ) Hydrogen bonding in water
Strong intermolecular hydrogen bonds between H₂O molecules require more energy to break. H₂S actually has the larger molar mass, so mass cannot explain the difference.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following molecules is paramagnetic?
सही उत्तर: ख) O₂
MO theory shows O₂ has two unpaired electrons in degenerate π* orbitals, so it is paramagnetic. N₂, F₂ and CO have all electrons paired.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The bond order of the O₂⁺ ion is:
सही उत्तर: ग) 2.5
Removing one electron from an antibonding π* orbital of O₂ (bond order 2) gives O₂⁺ with bond order (10 − 5)/2 = 2.5. 1.5 is the bond order of O₂⁻.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following molecules has zero dipole moment?
सही उत्तर: ख) CO₂
CO₂ is linear, so the two equal C=O bond dipoles cancel each other. H₂O is bent, so its bond dipoles do not cancel.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The hybridisation of phosphorus in PCl₅ is:
सही उत्तर: घ) sp³d
Phosphorus uses one s, three p and one d orbital to form five bonds, giving sp³d hybridisation and a trigonal bipyramidal shape. sp³d² corresponds to six bonds, as in SF₆.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The geometry of the SF₆ molecule is:
सही उत्तर: ख) Octahedral
Sulphur in SF₆ is sp³d² hybridised with six bond pairs, giving an octahedral geometry. Trigonal bipyramidal geometry is seen in PCl₅ (sp³d).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The H–O–H bond angle in a water molecule is approximately:
सही उत्तर: ग) 104.5°
Two lone pairs on oxygen compress the tetrahedral angle down to about 104.5°. 107° is the bond angle in NH₃, which has only one lone pair.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The shape of the ammonia (NH₃) molecule is:
सही उत्तर: ग) Trigonal pyramidal
N in NH₃ is sp³ hybridised with three bond pairs and one lone pair, giving a trigonal pyramidal shape. The electron-pair geometry is tetrahedral, but the molecular shape is not.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The series of lines in the hydrogen spectrum that lies in the visible region is the:
सही उत्तर: ग) Balmer series
Balmer lines arise from transitions ending at n = 2 and fall in the visible region. The Lyman series (ending at n = 1) lies in the ultraviolet.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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