इन्जिनियरिङ प्रवेश – Mathematics, Physics, Chemistry, English
इन्जिनियरिङ प्रवेश – Mathematics, Physics, Chemistry, English
Engineering Entrance – Mathematics, Physics, Chemistry & English · ३,८४१ प्रश्न
३,८४१ प्रश्न उपलब्ध। मोड छान्नुहोस्:
इन्जिनियरिङ 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 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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Which element has the most negative (highest) electron gain enthalpy?
सही उत्तर: ग) Chlorine
Chlorine has the highest electron affinity. Fluorine's value is lower because its small 2p subshell causes strong repulsion with the incoming electron.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Among B, C, N and O, the element with the highest first ionisation energy is:
सही उत्तर: ख) N
Nitrogen's half-filled 2p³ subshell is extra stable, so its first ionisation energy exceeds that of oxygen. Oxygen is lower because removing one paired 2p electron relieves electron repulsion.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Among Na, Mg, Al and Si, the element with the largest atomic radius is:
सही उत्तर: क) Na
Atomic radius decreases across a period as nuclear charge increases with the same shell, so sodium, at the start of period 3, is largest. Silicon is the smallest of the four.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of neutrons in an atom of ²³⁵U (atomic number 92) is:
सही उत्तर: घ) 143
Neutrons = mass number − atomic number = 235 − 92 = 143. 92 is the number of protons.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which pair of atoms are isotones (same number of neutrons)?
सही उत्तर: ग) ¹⁴C and ¹⁶O
¹⁴C has 14 − 6 = 8 neutrons and ¹⁶O has 16 − 8 = 8 neutrons, so they are isotones. ³⁵Cl and ³⁷Cl are isotopes (same Z, different neutrons).
💬 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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