रसायन विज्ञान – Chemistry MCQ
रसायन विज्ञान – कृषि/वन प्रवेश
Chemistry · Agriculture, Veterinary & Forestry Entrance · ४०९ प्रश्न
४०९ प्रश्न उपलब्ध। मोड छान्नुहोस्:
रसायन विज्ञान: 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 number of valence electrons in a nitrogen atom (Z = 7) is:
सही उत्तर: ग) 5
Configuration 2, 5: the outer shell has 5 electrons.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Copper sulphate crystals (blue vitriol) turn white on strong heating because:
सही उत्तर: ख) they lose their water of crystallisation
CuSO₄·5H₂O → CuSO₄ (white, anhydrous) + 5H₂O; adding water restores the blue colour.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Zinc reacts with hot concentrated sodium hydroxide solution to liberate:
सही उत्तर: ख) hydrogen
Zn + 2NaOH → Na₂ZnO₂ + H₂; zinc is amphoteric and reacts with both acids and strong bases.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The gas used in fire extinguishers because it is heavier than air and does not support combustion is:
सही उत्तर: क) carbon dioxide
CO₂ forms a blanket over the fire and cuts off the supply of oxygen.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Natural rubber is heated with sulphur to make it harder and more elastic. This process is called:
सही उत्तर: ख) vulcanisation
Sulphur forms cross-links between rubber chains.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Diamond and graphite are both forms of carbon, but only graphite conducts electricity because:
सही उत्तर: क) each carbon in graphite has one free (delocalised) electron
In graphite each sp² carbon uses three electrons in bonding, leaving one delocalised electron; in diamond all four are used.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Packets of potato chips are filled with nitrogen gas mainly to:
सही उत्तर: घ) prevent oxidation (rancidity) of the oil
Nitrogen is inert and displaces oxygen, so fats in the chips do not oxidise and turn rancid.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Sodium metal is stored under kerosene because:
सही उत्तर: क) it reacts vigorously with oxygen and moisture in air
Kerosene keeps air and water away from the highly reactive metal.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Stainless steel resists rusting because it contains, besides iron and carbon:
सही उत्तर: ख) chromium (with nickel)
Chromium forms a thin protective oxide layer on the surface that prevents further corrosion.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The non-metal that is a liquid at room temperature is:
सही उत्तर: घ) bromine
Bromine is a reddish-brown liquid; chlorine is a gas and iodine a solid.
💬 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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