रसायन विज्ञान (Chemistry) – Chemistry MCQ
रसायन विज्ञान (Chemistry) – इन्जिनियरिङ प्रवेश
Chemistry · Engineering Entrance – Mathematics, Physics, Chemistry & English · ७२८ प्रश्न
७२८ 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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The pH of a 0.01 M NaOH solution at 25 °C is:
सही उत्तर: ग) 12
[OH⁻] = 10⁻² M gives pOH = 2, so pH = 14 − 2 = 12. A pH of 2 is the pOH mistakenly reported as pH.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For which reaction is Kp equal to Kc?
सही उत्तर: क) H₂(g) + I₂(g) ⇌ 2HI(g)
Kp = Kc(RT)^Δn, and for H₂ + I₂ ⇌ 2HI, Δn = 2 − 2 = 0, so Kp = Kc. The other reactions involve a change in the number of gaseous moles.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For the isothermal expansion of an ideal gas, the change in internal energy (ΔU) is:
सही उत्तर: घ) Zero
The internal energy of an ideal gas depends only on temperature, so at constant temperature ΔU = 0. The heat absorbed then equals the work done by the gas, but ΔU itself is zero.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which process is accompanied by an increase in entropy?
सही उत्तर: ग) Melting of ice
Melting turns an ordered solid into a more disordered liquid, increasing entropy. Freezing and condensation both increase order, so entropy decreases.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For the reaction N₂(g) + 3H₂(g) → 2NH₃(g), the relation between ΔH and ΔU is:
सही उत्तर: ख) ΔH = ΔU − 2RT
ΔH = ΔU + Δn_g RT with Δn_g = 2 − 4 = −2, giving ΔH = ΔU − 2RT. −4RT counts only the reactant moles and forgets the 2 mol of product.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the van der Waals equation, the constant 'a' is a measure of:
सही उत्तर: क) Intermolecular attractive forces
The term a n²/V² corrects pressure for attractive forces between molecules. The constant 'b' corrects for the finite volume of molecules.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A real gas behaves most like an ideal gas under conditions of:
सही उत्तर: घ) High temperature and low pressure
At high temperature intermolecular attractions matter less, and at low pressure the molecules' own volume is negligible. Low temperature and high pressure cause the largest deviations (and favour liquefaction).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The ratio of the rates of diffusion of H₂ and O₂ under the same conditions is:
सही उत्तर: ग) 4 : 1
By Graham's law r ∝ 1/√M, so r(H₂)/r(O₂) = √(32/2) = √16 = 4. 16 : 1 forgets to take the square root.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A gas at 27 °C is heated at constant pressure. At what temperature will its volume become double?
सही उत्तर: ख) 327 °C
By Charles's law V ∝ T (in kelvin): 300 K must become 600 K, which is 327 °C. 54 °C comes from doubling the Celsius temperature, which is wrong.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of sigma (σ) and pi (π) bonds in an ethene (C₂H₄) molecule is:
सही उत्तर: क) 5 σ and 1 π
Ethene has four C–H σ bonds and a C=C double bond made of one σ and one π bond, giving 5 σ and 1 π. Forgetting the C–C σ bond gives the wrong count of 4 σ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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