रसायन विज्ञान – Chemistry MCQ
रसायन विज्ञान – कृषि/वन प्रवेश
Chemistry · Agriculture, Veterinary & Forestry Entrance · ३९२ प्रश्न
३९२ 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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In the Haber process for the manufacture of ammonia, the catalyst used is:
सही उत्तर: क) Iron
Finely divided iron (with molybdenum or K₂O/Al₂O₃ as promoters) catalyses N₂ + 3H₂ ⇌ 2NH₃. V₂O₅ is used in the contact process for H₂SO₄.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of orbitals present in a d-subshell is:
सही उत्तर: क) 5
For l = 2, m takes values −2 to +2, giving 5 orbitals that hold up to 10 electrons. A p-subshell has 3 orbitals and an f-subshell 7.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The most electronegative element in the periodic table is:
सही उत्तर: घ) Fluorine
Fluorine has the highest electronegativity (about 4.0 on the Pauling scale). Chlorine has the highest electron affinity, which is a different property.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The unusually high boiling point of water compared with H₂S is due to:
सही उत्तर: क) Hydrogen bonding
Strong intermolecular hydrogen bonds between H₂O molecules require more energy to break. H₂S is actually heavier than water, so molar mass cannot explain it.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The unit of the rate constant of a first-order reaction is:
सही उत्तर: ख) s⁻¹
For first order, rate = k[A], so k = rate/[A] has units of time⁻¹. mol L⁻¹ s⁻¹ is the unit for a zero-order rate constant.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the pOH of a solution at 25 °C is 4, its pH is:
सही उत्तर: क) 10
pH + pOH = 14 at 25 °C, so pH = 14 − 4 = 10. The solution is basic.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Tollens' reagent (ammoniacal silver nitrate) gives a silver mirror with:
सही उत्तर: घ) Aldehydes
Aldehydes are easily oxidised and reduce Ag⁺ to metallic silver, forming a mirror. Simple ketones like acetone do not respond, so the test distinguishes the two.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The metal ion present at the centre of the chlorophyll molecule is:
सही उत्तर: क) Magnesium
Chlorophyll is a porphyrin complex with Mg²⁺ at its centre, which is why Mg deficiency causes yellowing (chlorosis). Haemoglobin contains iron instead.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The bond order of the O₂ molecule according to molecular orbital theory is:
सही उत्तर: ख) 2
O₂ has 10 bonding and 6 antibonding valence electrons, so bond order = (10 − 6)/2 = 2. A bond order of 3 belongs to N₂.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The scattering of light by colloidal particles, making the path of a beam visible, is called the:
सही उत्तर: ग) Tyndall effect
Colloidal particles are large enough to scatter light, so a beam through a sol becomes visible; true solutions do not show this. Brownian motion is the random zig-zag movement of colloidal particles.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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