रसायन विज्ञान (Chemistry) – Chemistry MCQ
रसायन विज्ञान (Chemistry) – CEE प्रवेश
Chemistry · Medical Entrance (CEE) – Physics, Chemistry, Biology & MAT · ४१० प्रश्न
४१० 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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Nessler's reagent (alkaline K₂HgI₄) gives a brown precipitate or colour with:
सही उत्तर: क) ammonia or ammonium ions
Nessler's reagent reacts with NH₃ (from NH₄⁺ in alkali) to give a brown precipitate (iodide of Millon's base); it is used to detect ammonia in water.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Among the carbonates of group 2, the one with the highest thermal stability is:
सही उत्तर: ख) BaCO₃
Larger cations polarise the carbonate ion less, so decomposition temperature rises down the group; BaCO₃ is the most stable.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Among the hydroxides of the alkaline earth metals, the one most soluble in water is:
सही उत्तर: ग) Ba(OH)₂
Solubility of group 2 hydroxides increases down the group because lattice energy falls faster than hydration energy; Ba(OH)₂ is the most soluble.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The approximate strength of '20 volume' hydrogen peroxide solution in grams of H₂O₂ per 100 mL is:
सही उत्तर: घ) 6.1 g
1 L gives 20 L O₂ at STP = 20/22.4 mol O₂, from 2 × 20/22.4 = 1.79 mol H₂O₂ = 60.7 g/L, i.e. about 6.1 g per 100 mL.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the electrolytic refining of copper, the impure copper is made the:
सही उत्तर: ख) anode
Impure copper is the anode and dissolves as Cu²⁺; pure copper deposits on the thin pure-copper cathode, and impurities collect as anode mud.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The van Arkel (iodide) method is used for obtaining ultrapure:
सही उत्तर: ख) zirconium and titanium
Impure Zr or Ti is heated with iodine to form a volatile iodide, which is decomposed on a hot tungsten filament to deposit the pure metal.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of unpaired electrons in the low-spin complex ion [Fe(CN)₆]³⁻ is:
सही उत्तर: क) 1
Fe³⁺ is d⁵; CN⁻ is a strong-field ligand, so all five electrons go into the t₂g set (t₂g⁵), leaving one unpaired electron.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of geometrical isomers of the octahedral complex [Co(NH₃)₃Cl₃] is:
सही उत्तर: क) 2
An MA₃B₃ octahedral complex exists as two geometrical isomers: facial (fac) and meridional (mer).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The effective atomic number (EAN) of iron in [Fe(CN)₆]⁴⁻ is (Z of Fe = 26):
सही उत्तर: घ) 36
Fe²⁺ has 26 − 2 = 24 electrons; six CN⁻ ligands donate 12 electrons, so EAN = 24 + 12 = 36 (krypton configuration).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the old 'breath analyser' test for drunken driving, the colour change observed when alcohol is present is:
सही उत्तर: ग) orange to green
Acidified K₂Cr₂O₇ (orange, Cr⁶⁺) oxidises ethanol in the breath and is itself reduced to Cr³⁺, which is green.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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