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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Which hydrogen halide is the strongest acid in aqueous solution?
सही उत्तर: क) HI
Acid strength increases HF < HCl < HBr < HI because the H–X bond becomes weaker as the halogen gets larger. HF is weakest because of its very strong H–F bond.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Sodium metal is stored under kerosene because it:
सही उत्तर: घ) Reacts vigorously with air and moisture
Sodium reacts rapidly with oxygen and violently with water, so it is kept under kerosene, with which it does not react. White phosphorus, by contrast, is stored under water.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Froth flotation is mainly used for concentrating:
सही उत्तर: ख) Sulphide ores
In froth flotation, sulphide ore particles are wetted by oil and carried up in the froth while gangue is wetted by water and sinks. Oxide ores are usually concentrated by gravity or magnetic methods or by leaching.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Galena is an ore of:
सही उत्तर: क) Lead (PbS)
Galena is lead sulphide, PbS, the chief ore of lead. ZnS is zinc blende.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The chemical formula of haematite is:
सही उत्तर: घ) Fe₂O₃
Haematite is iron(III) oxide, Fe₂O₃. Fe₃O₄ is magnetite.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The chief ore of aluminium is:
सही उत्तर: ग) Bauxite
Bauxite (Al₂O₃·xH₂O) is the main ore of aluminium. Haematite is an iron ore and galena is a lead ore.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Ostwald's process is used for the manufacture of:
सही उत्तर: ख) Nitric acid
Ostwald's process oxidises ammonia over a platinum catalyst to NO, which is converted to HNO₃. Sodium carbonate is made by the Solvay process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the contact process for manufacturing sulphuric acid, the catalyst used to oxidise SO₂ to SO₃ is:
सही उत्तर: क) V₂O₅
Vanadium pentoxide catalyses 2SO₂ + O₂ ⇌ 2SO₃ in the contact process. Iron is the catalyst in the Haber process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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100 mL of a 1 M HCl solution is diluted with water to 500 mL. The new molarity is:
सही उत्तर: ख) 0.2 M
Using M₁V₁ = M₂V₂: 1 × 100 = M₂ × 500, so M₂ = 0.2 M. 0.25 M would result if 400 mL were taken as the final volume.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The mass of oxygen required for complete combustion of 16 g of methane (CH₄ + 2O₂ → CO₂ + 2H₂O) is:
सही उत्तर: क) 64 g
16 g CH₄ = 1 mol, which needs 2 mol O₂ = 64 g. 32 g is the mass of only 1 mol of O₂; 44 g is the mass of CO₂ formed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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