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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An SN2 reaction at a chiral carbon proceeds with:
सही उत्तर: क) Inversion of configuration
In SN2 the nucleophile attacks from the side opposite the leaving group in one step, causing Walden inversion. Racemisation and carbocation formation are typical of SN1.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The bond linking amino acids in proteins is the:
सही उत्तर: घ) Peptide bond (–CO–NH–)
Amino acids join through amide links between –COOH of one and –NH₂ of another, called peptide bonds. Glycosidic bonds link monosaccharides in carbohydrates.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Glucose is classified as an:
सही उत्तर: ग) Aldohexose
Glucose has six carbons and an aldehyde (–CHO) group, so it is an aldohexose. Fructose, with a ketone group, is a ketohexose.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Natural rubber is a polymer of:
सही उत्तर: ख) Isoprene
Natural rubber is cis-1,4-polyisoprene (2-methylbuta-1,3-diene). Chloroprene polymerises to the synthetic rubber neoprene.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Nylon-6,6 is formed by condensation polymerisation of hexamethylenediamine with:
सही उत्तर: क) Adipic acid
Hexamethylenediamine and adipic acid each have six carbons and form polyamide nylon-6,6. Caprolactam is the monomer of nylon-6.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The monomer of polyvinyl chloride (PVC) is:
सही उत्तर: घ) CH₂=CHCl
PVC is formed by addition polymerisation of vinyl chloride (chloroethene). CF₂=CF₂ is the monomer of Teflon.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction of a carboxylic acid with an alcohol in the presence of conc. H₂SO₄ to form an ester is called:
सही उत्तर: ग) Esterification
Acid-catalysed reaction of RCOOH with R'OH gives RCOOR' + H₂O (Fischer esterification). Saponification is the reverse type of reaction, alkaline hydrolysis of an ester.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Acetylene (ethyne) is prepared in the laboratory by the action of water on:
सही उत्तर: ख) Calcium carbide
CaC₂ + 2H₂O → C₂H₂ + Ca(OH)₂. Aluminium carbide with water gives methane instead.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The order of stability of carbocations is:
सही उत्तर: क) 3° > 2° > 1° > CH₃⁺
Alkyl groups stabilise a carbocation by the +I effect and hyperconjugation, so tertiary is most stable and methyl least. Free radicals follow the same order.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which compound shows geometrical (cis–trans) isomerism?
सही उत्तर: घ) But-2-ene
In but-2-ene each double-bonded carbon has two different groups (H and CH₃), allowing cis and trans forms. In but-1-ene, one double-bonded carbon has two hydrogens, so no geometrical isomers exist.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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