IT प्रवेश – B.Sc. CSIT, BIT, BCA
IT प्रवेश – B.Sc. CSIT, BIT, BCA
IT Entrance – B.Sc. CSIT, BIT & BCA · २,६०५ प्रश्न
२,६०५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
IT 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 peroxide (Kharasch) effect, which gives anti-Markovnikov addition, is observed with:
सही उत्तर: क) HBr only
Only HBr shows the peroxide effect, because its free-radical chain steps are energetically favourable. For HCl and HI one of the radical steps is unfavourable.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Addition of HBr to propene (with no peroxide) mainly gives:
सही उत्तर: क) 2-Bromopropane
By Markovnikov's rule, H adds to the carbon that already has more H atoms, and Br goes to the middle carbon through the more stable secondary carbocation. 1-Bromopropane is the major product only when a peroxide is present.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of π electrons in a benzene molecule is:
सही उत्तर: ग) 6
Benzene has three C=C π bonds with two electrons each, giving 6 delocalized π electrons, which satisfies Hückel's (4n + 2) rule for n = 1. 3 is the number of π bonds, not electrons.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The general formula of alkynes is:
सही उत्तर: ख) CₙH₂ₙ₋₂
Alkynes have one C≡C triple bond, which means four fewer H atoms than alkanes (CₙH₂ₙ₊₂). CₙH₂ₙ is the general formula of alkenes (and cycloalkanes).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Galvanization of iron means coating it with:
सही उत्तर: क) Zinc
A zinc coating protects iron even when scratched, because the more reactive zinc corrodes first (sacrificial protection). Coating with tin is called tinning.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Froth flotation is mainly used to concentrate:
सही उत्तर: ख) Sulphide ores
Sulphide ore particles are wetted by oil and carried up in the froth, while the gangue is wetted by water and sinks. Oxide ores are usually concentrated by gravity or magnetic separation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Acid rain is mainly caused by atmospheric:
सही उत्तर: क) Oxides of sulphur and nitrogen
SO₂ and NOₓ dissolve in rainwater to form sulphuric and nitric acids, lowering the pH of rain. CFCs are linked to ozone depletion, not acid rain.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The Solvay (ammonia-soda) process is used to manufacture:
सही उत्तर: क) Sodium carbonate
The Solvay process makes Na₂CO₃ (washing soda) from brine, ammonia and CO₂. NaOH is made industrially by electrolysis of brine (chlor-alkali process).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The Ostwald process is used for the manufacture of:
सही उत्तर: घ) Nitric acid
In the Ostwald process, ammonia is catalytically oxidized over platinum to NO, which is then converted to HNO₃. Ammonia itself is made by the Haber process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The most abundant element in the Earth's crust by mass is:
सही उत्तर: ग) Oxygen
Oxygen makes up nearly half of the Earth's crust by mass, followed by silicon. Aluminium is the most abundant metal in the crust.
💬 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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