आईओई इन्जिनियरिङ प्रवेश (त्रिवि) BE / B.Arch प्रवेश परीक्षा तयारी
आईओई इन्जिनियरिङ प्रवेश (त्रिवि) – BE / B.Arch प्रवेश परीक्षा
IOE BE / B.Arch Entrance · IOE Entrance (TU)
३,८४१ प्रश्न उपलब्ध। मोड छान्नुहोस्:
BE/B.Arch 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 carbylamine (isocyanide) test is given by:
सही उत्तर: क) Primary amines
Primary amines heated with chloroform and alcoholic KOH give foul-smelling isocyanides (RNC). Secondary and tertiary amines do not give this test.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Treating an acid amide with Br₂ and aqueous NaOH (Hofmann bromamide reaction) gives:
सही उत्तर: घ) A primary amine with one carbon fewer
In the Hofmann bromamide degradation, RCONH₂ → RNH₂, losing the carbonyl carbon as carbonate. Reduction of an amide with LiAlH₄ instead gives an amine with the same number of carbons.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the Lucas test, which type of alcohol produces turbidity immediately at room temperature?
सही उत्तर: ख) Tertiary alcohol
Tertiary alcohols react fastest with conc. HCl/ZnCl₂ because they form the most stable carbocation, giving immediate cloudiness. Secondary alcohols take about 5 minutes, and primary alcohols show no turbidity at room temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which alcohol gives a positive iodoform test?
सही उत्तर: क) Ethanol
Ethanol contains the CH₃CH(OH)– group, which is oxidised to a CH₃CO– group and gives yellow iodoform (CHI₃). Methanol lacks this group and does not give the test.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which compound gives a silver mirror with Tollens' reagent?
सही उत्तर: घ) Ethanal (acetaldehyde)
Aldehydes reduce ammoniacal silver nitrate to metallic silver, forming a silver mirror. Ketones like acetone generally do not respond to Tollens' test.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Anhydrous AlCl₃ is used as a catalyst in:
सही उत्तर: ग) Friedel–Crafts alkylation
Anhydrous AlCl₃, a Lewis acid, generates the carbocation (or acylium ion) electrophile in Friedel–Crafts reactions. Hydrogenation uses metal catalysts such as Ni, Pt or Pd.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The electrophile in the nitration of benzene with a mixture of conc. HNO₃ and conc. H₂SO₄ is:
सही उत्तर: ख) NO₂⁺
Sulphuric acid protonates nitric acid, which loses water to form the nitronium ion NO₂⁺, the attacking electrophile. NO₃⁻ and NO₂⁻ are anions and cannot act as electrophiles towards the electron-rich ring.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction of an alkyl halide with sodium metal in dry ether to give a higher alkane is called:
सही उत्तर: क) Wurtz reaction
In the Wurtz reaction 2RX + 2Na → R–R + 2NaX in dry ether. The Sandmeyer reaction converts diazonium salts to aryl halides using copper(I) salts.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Addition of HBr to propene in the presence of an organic peroxide gives mainly:
सही उत्तर: घ) 1-Bromopropane
Peroxide causes free-radical addition (Kharasch or peroxide effect), giving the anti-Markovnikov product 1-bromopropane. This effect is seen only with HBr, not HCl or HI.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Addition of HBr to propene in the absence of peroxide gives mainly:
सही उत्तर: ग) 2-Bromopropane
By Markovnikov's rule, H adds to the carbon with more hydrogens and Br to the more substituted carbon, through the more stable secondary carbocation. 1-Bromopropane forms in the presence of peroxide (anti-Markovnikov addition).
💬 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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