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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When a protein is denatured (e.g. by heat), the structure that remains intact is its:
सही उत्तर: ग) primary structure
Denaturation disrupts hydrogen bonds and other weak interactions, but the peptide bonds that make up the amino-acid sequence remain.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Benzaldehyde heated with acetic anhydride and sodium acetate (Perkin reaction) gives:
सही उत्तर: ख) cinnamic acid
The Perkin condensation of an aromatic aldehyde with an acid anhydride gives an α,β-unsaturated acid: C₆H₅CH=CHCOOH.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In aqueous solution, the correct order of basic strength of methylamines is:
सही उत्तर: ग) (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃
In water, the combined effects of +I, hydration of the ammonium ion and steric hindrance make the secondary amine strongest and the tertiary amine weaker than the primary.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Hydroboration–oxidation of propene (B₂H₆, then H₂O₂/OH⁻) gives mainly:
सही उत्तर: घ) propan-1-ol
Boron adds to the less substituted carbon and is replaced by OH, giving the anti-Markovnikov alcohol, propan-1-ol.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Among the groups –NO₂, –CN, –COOH and –F, the one with the strongest –I (electron-withdrawing inductive) effect is:
सही उत्तर: ख) –NO₂
The standard order of –I effect is –NO₂ > –CN > –COOH > –F > –Cl > –Br > –I.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Wilkinson's catalyst, used for homogeneous hydrogenation of alkenes, is a complex of:
सही उत्तर: ख) rhodium
Wilkinson's catalyst is [RhCl(PPh₃)₃], chloridotris(triphenylphosphine)rhodium(I).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The octahedral complex ion [Co(NH₃)₄Cl₂]⁺ exists in how many geometrical isomers?
सही उत्तर: क) 2
An MA₄B₂ octahedral complex has two geometrical isomers: cis and trans.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following is an ambidentate ligand?
सही उत्तर: घ) NO₂⁻
NO₂⁻ can bind through N (nitro) or O (nitrito); ligands that can bind through either of two donor atoms are ambidentate.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The IUPAC name of K₃[Fe(CN)₆] is:
सही उत्तर: ग) potassium hexacyanoferrate(III)
Fe is +3 (3 + x − 6 = 0), and in an anionic complex the metal takes the -ate ending: hexacyanoferrate(III).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the cyanide process (leaching) for extracting silver and gold, the ore is treated with:
सही उत्तर: ग) a dilute solution of NaCN in the presence of air
The metal dissolves as a soluble complex such as [Ag(CN)₂]⁻ or [Au(CN)₂]⁻ and is then displaced by zinc.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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