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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For coagulating a negatively charged colloidal sol (e.g. As₂S₃ sol), the most effective ion is:
सही उत्तर: ख) Al³⁺
By the Hardy–Schulze rule, coagulating power increases with the charge of the oppositely charged ion, so Al³⁺ is most effective. PO₄³⁻ carries the same sign as the sol and would coagulate a positive sol instead.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The scattering of light by colloidal particles is known as:
सही उत्तर: ग) Tyndall effect
Colloidal particles are large enough to scatter light, making the beam's path visible (Tyndall effect). Brownian motion is the random zig-zag movement of colloidal particles.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Raoult's law, the relative lowering of vapour pressure of a dilute solution is equal to:
सही उत्तर: क) Mole fraction of the solute
(P° − P)/P° = x(solute) for a solution of a non-volatile solute. The vapour pressure of the solution itself is proportional to the mole fraction of the solvent.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following 0.1 m aqueous solutions has the highest boiling point?
सही उत्तर: ग) Al₂(SO₄)₃
Boiling point elevation depends on the number of solute particles; Al₂(SO₄)₃ gives 5 ions (i = 5). Glucose does not dissociate (i = 1) and has the smallest effect.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Assuming complete dissociation, the van't Hoff factor (i) for K₂SO₄ is:
सही उत्तर: क) 3
K₂SO₄ → 2K⁺ + SO₄²⁻, giving 3 ions per formula unit, so i = 3. For NaCl, i would be 2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following is the strongest reducing agent in aqueous solution?
सही उत्तर: घ) Li
Lithium has the most negative standard reduction potential (about −3.04 V), so it loses electrons most readily in water. This is due to the very high hydration energy of the small Li⁺ ion.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Given E°(Cu²⁺/Cu) = +0.34 V and E°(Zn²⁺/Zn) = −0.76 V, the standard EMF of the Daniell cell is:
सही उत्तर: ख) 1.10 V
E°cell = E°cathode − E°anode = 0.34 − (−0.76) = 1.10 V. Taking the difference of the magnitudes (0.76 − 0.34) gives the incorrect 0.42 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The mass of silver deposited when 1 faraday of electricity is passed through AgNO₃ solution is (Ag = 108):
सही उत्तर: ख) 108 g
Ag⁺ + e⁻ → Ag, so 1 F (1 mol of electrons) deposits 1 mol = 108 g of silver. 54 g would apply to a divalent ion of the same atomic mass.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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One faraday of electricity is approximately equal to:
सही उत्तर: घ) 96500 C
One faraday is the charge of one mole of electrons: 6.022 × 10²³ × 1.602 × 10⁻¹⁹ ≈ 96500 C. 1.6 × 10⁻¹⁹ C is the charge of a single electron.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A first-order reaction has a half-life of 20 min. The time required for 75% completion is:
सही उत्तर: क) 40 min
75% completion leaves 25% (¼) of the reactant, which takes two half-lives: 2 × 20 = 40 min. 30 min wrongly assumes the reaction proceeds linearly.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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