रसायन विज्ञान – Chemistry MCQ
रसायन विज्ञान – IT प्रवेश
Chemistry · IT Entrance – B.Sc. CSIT, BIT & BCA · ६४१ प्रश्न
६४१ 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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Which mixture forms an acidic buffer solution?
सही उत्तर: ख) CH₃COOH and CH₃COONa
An acidic buffer is a weak acid with its salt of a strong base. NH₄OH + NH₄Cl is a basic buffer, and HCl + NaCl involves a strong acid, which cannot form a buffer.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The conjugate base of NH₄⁺ is:
सही उत्तर: ख) NH₃
A conjugate base is formed when an acid loses one proton: NH₄⁺ − H⁺ = NH₃. NH₂⁻ is the conjugate base of NH₃, not of NH₄⁺.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Adding a catalyst to a reaction at equilibrium:
सही उत्तर: ग) Helps equilibrium be reached faster without changing the equilibrium constant
A catalyst lowers the activation energy of the forward and reverse reactions equally, so equilibrium is reached faster but K stays the same. It does not change the equilibrium yield.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), the relation between Kp and Kc is:
सही उत्तर: ख) Kp = Kc(RT)⁻²
Kp = Kc(RT)^Δn, with Δn = 2 − 4 = −2. Kp = Kc only when Δn = 0, as in H₂ + I₂ ⇌ 2HI.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), ΔH < 0, the yield of ammonia is increased by:
सही उत्तर: क) Increasing the pressure
The forward reaction reduces the number of gas moles (4 → 2), so higher pressure shifts the equilibrium to the right (Le Chatelier's principle). Since the reaction is exothermic, raising the temperature lowers the yield.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The mass of 11.2 L of O₂ gas at STP is:
सही उत्तर: क) 16 g
11.2 L at STP is 0.5 mol, and 0.5 × 32 g/mol = 16 g. 32 g is the mass of a full mole (22.4 L).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When 4 g of H₂ reacts with 16 g of O₂ to form water (2H₂ + O₂ → 2H₂O), the mass of water formed is:
सही उत्तर: क) 18 g
4 g H₂ = 2 mol and 16 g O₂ = 0.5 mol; 0.5 mol O₂ needs only 1 mol H₂, so O₂ is the limiting reagent and gives 1 mol (18 g) of water. 36 g would assume H₂ is fully used.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The empirical formula of glucose (C₆H₁₂O₆) is:
सही उत्तर: घ) CH₂O
Dividing the subscripts 6, 12, 6 by their highest common factor 6 gives CH₂O. C₆H₁₂O₆ is the molecular formula.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The percentage of nitrogen by mass in urea, CO(NH₂)₂, is about:
सही उत्तर: ख) 46.7%
Molar mass of urea = 60 g/mol and it contains 28 g of nitrogen, so %N = 28/60 × 100 ≈ 46.7%. 28% confuses the mass of nitrogen with its percentage.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The equivalent weight of H₂SO₄ (molar mass 98) as an acid is:
सही उत्तर: ग) 49
Equivalent weight = molar mass / basicity = 98/2 = 49. 32.7 would come from dividing by 3, which is correct for H₃PO₄.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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