त्रिवि IT प्रवेश BIT र BCA प्रवेश तयारी
त्रिवि IT प्रवेश – BIT र BCA प्रवेश
TU BIT & BCA Entrance · TU IT Entrance (B.Sc. CSIT, BIT, BCA)
२,६०५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
IT 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 catalyst used in Friedel–Crafts alkylation of benzene is:
सही उत्तर: ग) Anhydrous AlCl₃
Anhydrous AlCl₃, a Lewis acid, produces the carbocation electrophile from an alkyl halide. Pd/BaSO₄ is the Rosenmund catalyst, used to reduce acid chlorides to aldehydes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Phenol is more acidic than ethanol because:
सही उत्तर: घ) The phenoxide ion is stabilized by resonance
The negative charge on the phenoxide ion is delocalized over the benzene ring, which stabilizes it and favours ionization. The ethoxide ion has no resonance and is destabilized by the electron-donating ethyl group.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The monomer of PVC is:
सही उत्तर: ख) Vinyl chloride (CH₂=CHCl)
PVC (polyvinyl chloride) is made by addition polymerization of vinyl chloride. Tetrafluoroethylene is the monomer of Teflon.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Nylon-6,6 is made from:
सही उत्तर: क) Hexamethylenediamine and adipic acid
Nylon-6,6 is a condensation polymer of hexamethylenediamine and adipic acid, both with six carbons. Caprolactam gives nylon-6, and ethylene glycol + terephthalic acid gives terylene (PET).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the alcoholic fermentation of glucose by yeast, the enzyme zymase converts glucose into:
सही उत्तर: ग) Ethanol and carbon dioxide
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂, catalysed by zymase. Lactic acid is the product of fermentation in muscles and in milk souring.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Saponification is the:
सही उत्तर: क) Alkaline hydrolysis of fats or oils to form soap
Heating a fat (a triglyceride ester) with NaOH gives glycerol and the sodium salts of fatty acids, which are soap. Esterification is the reverse type of reaction, forming an ester from an acid and an alcohol.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A silver mirror formed with Tollens' reagent indicates the presence of:
सही उत्तर: घ) An aldehyde
Aldehydes reduce ammoniacal silver nitrate to metallic silver, which forms a mirror on the glass. Simple ketones do not give this test, which is how the two are distinguished.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The Lucas test is used to distinguish between:
सही उत्तर: घ) Primary, secondary and tertiary alcohols
The Lucas reagent (conc. HCl + anhydrous ZnCl₂) gives turbidity immediately with tertiary alcohols, in a few minutes with secondary alcohols, and not at room temperature with primary ones. Amines are distinguished by the Hinsberg test.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following gives a positive iodoform test?
सही उत्तर: घ) Ethanol
Ethanol is oxidized to ethanal (which has CH₃CO–), so it forms yellow CHI₃ with I₂ and NaOH. Methanol does not have a CH₃CH(OH)– group and gives a negative test.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction of an alkyl halide with sodium metal in dry ether to form a higher alkane is called:
सही उत्तर: क) Wurtz reaction
In the Wurtz reaction, 2R–X + 2Na → R–R + 2NaX, which doubles the carbon chain. The Wurtz–Fittig reaction is the related version that uses an aryl halide.
💬 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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