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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If the equilibrium constant of A + B ⇌ C is K, the equilibrium constant of 2A + 2B ⇌ 2C at the same temperature is:
सही उत्तर: ग) K²
Multiplying a balanced equation by n raises its equilibrium constant to the power n, so the constant becomes K².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For the equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g), adding more N₂ at constant volume and temperature:
सही उत्तर: ख) shifts the equilibrium to the right
By Le Chatelier's principle, adding a reactant shifts the equilibrium forward to consume it; K is unchanged at constant temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the equilibrium constant K of a reaction at a given temperature is greater than 1, the standard Gibbs energy change ΔG° is:
सही उत्तर: क) negative
ΔG° = −RT ln K; for K > 1, ln K > 0, so ΔG° is negative.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to the third law of thermodynamics, the entropy of a perfectly crystalline substance at absolute zero is:
सही उत्तर: घ) zero
The third law states that a perfect crystal at 0 K has perfect order and zero entropy.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a reaction at equilibrium at constant temperature and pressure, the Gibbs free energy change ΔG is:
सही उत्तर: ग) zero
At equilibrium there is no net driving force, so ΔG = 0.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Hess's law of constant heat summation is based on the fact that enthalpy change:
सही उत्तर: ख) is a state function, independent of the path
Since H is a state function, ΔH for a reaction is the same whether it occurs in one step or several.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Because acetic acid dimerises in benzene, its molar mass determined from a colligative property in benzene is about:
सही उत्तर: क) 120 g/mol
Two CH₃COOH molecules associate by hydrogen bonding, so i ≈ 0.5 and the apparent molar mass is about 2 × 60 = 120 g/mol.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For an ideal solution, which of the following is true?
सही उत्तर: घ) ΔH_mix = 0 and ΔV_mix = 0
An ideal solution obeys Raoult's law at all compositions, with no heat change and no volume change on mixing.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 0.5 molal aqueous urea solution has an elevation in boiling point of (K_b of water = 0.52 K kg mol⁻¹):
सही उत्तर: ग) 0.26 K
ΔT_b = K_b × m = 0.52 × 0.5 = 0.26 K (urea does not dissociate, i = 1).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Liquid mixtures that boil at a constant temperature and distil without change in composition are called:
सही उत्तर: ख) azeotropes
Azeotropes have the same composition in liquid and vapour phases, so they cannot be separated by fractional distillation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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