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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The process of converting ammonia into nitric oxide is industrially important. What is the primary reason this conversion is carried out?
सही उत्तर: ख) To reduce the production of unwanted byproducts like nitrogen dioxide
The main reason for converting ammonia to nitric oxide industrially is to minimize the formation of nitrogen dioxide (NO₂), a significant pollutant. Option A is incorrect because oxygen concentration isn't the primary factor; B correctly identifies NO₂ reduction, C is false as temperature changes are typically managed via catalysts, and D inaccurately describes fertilizer synthesis.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The rate constant for the decomposition of hydrogen iodide (HI) at 100°C is 3.5 x 10⁻³ s⁻¹. If the initial concentration of HI is 0.5 M, what will be the concentration of HI after 10 seconds?
सही उत्तर: क) 0.45 M
This question tests understanding of first-order kinetics. The rate law is Rate = k[HI]. Calculating the concentration change over 10 seconds using the given rate constant and initial concentration provides the correct answer (0.45 M). Options B, C, and D are incorrect because they do not accurately apply the integrated rate law for a first-order reaction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The addition of a small amount of potassium iodide (KI) to a solution containing silver nitrate (AgNO₃) results in the formation of a pale yellow precipitate. What is the primary reason for this observation?
सही उत्तर: ख) The reaction is exothermic and generates heat that causes light emission
This demonstrates the formation of a complex ion [AgI], which is weakly coloured in dilute solutions. The other options are incorrect or do not explain the pale yellow colour.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the major product formed when propanal (CH₃CHO) reacts with sodium hydroxide (NaOH)?
सही उत्तर: ग) 1-propanol
The reaction of an aldehyde with a base like NaOH proceeds via nucleophilic addition followed by protonation, resulting in the formation of a primary alcohol (1-propanol). The other options are incorrect products of this specific reaction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements best explains why NaCl is soluble in water?
सही उत्तर: ख) NaCl forms strong ion-dipole interactions with water molecules
The high dielectric constant of water allows it to effectively stabilize the dissolved ions through strong ion-dipole interactions, overcoming the lattice energy of NaCl. The other options describe inaccurate or irrelevant effects.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The process of converting primary alcohols to aldehydes using mild alkali metal hydrides like NaBH₄ is called ______.
सही उत्तर: क) Reduction
This describes the selective reduction of alcohols to aldehydes. The other options represent fundamentally different chemical processes (ester formation, breaking ester bonds, and oxidation respectively).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements regarding carbonates of Group 2 metals is most accurate? (a) Calcium carbonate (CaCO₃) is the least thermally stable due to its larger size. (b) Magnesium carbonate (MgCO₃) exhibits higher thermal stability compared to barium carbonate (BaCO₃). (c) The thermal stability of all carbonates of Group 2 metals is generally high due to strong lattice energies. (d) Sodium carbonate (Na₂CO₃) possesses the highest thermal stability owing to its ionic nature.
सही उत्तर: ख) (b)
The correct answer is (b). Magnesium carbonate (MgCO₃) has a smaller ionic radius and stronger electrostatic forces compared to barium carbonate (BaCO₃), leading to higher lattice energy and increased thermal stability. Option (a) is incorrect because calcium carbonate’s larger size actually *decreases* its stability. Options (c) and (d) are too general; the relative stability depends on specific ion sizes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The dissociation of acetic acid (CH₃COOH) in water is represented by HA ⇌ H⁺ + A⁻. If the concentration of H⁺ ions increases from 10⁻⁵ M to 10⁻³ M, what will be the new equilibrium constant (Ka) for this reaction?
सही उत्तर: घ) D: Changes abruptly depending on the concentration increase
Acetic acid dissociation is an equilibrium process. The Ka value depends on the concentrations of H⁺ and A⁻. An increase in [H⁺] will shift the equilibrium to the left, decreasing both [H⁺] and [A⁻], therefore reducing Ka. Option B is incorrect because it doesn't account for the equilibrium shift. Options A and D are incorrect as they suggest no change or an abrupt effect which isn’t true.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements best describes the role of a catalyst in a chemical reaction?\u003Cbr>(A) It is consumed during the reaction.\u003Cbr>Not it is consumed, but decreases the activation energy\u003Cbr>It increases the equilibrium constant\u003Cbr>It changes the enthalpy of the reaction
सही उत्तर: ख) Not it is consumed, but decreases the activation energy
A catalyst lowers the activation energy required for a chemical reaction to occur without being permanently altered itself. It speeds up the rate of the reaction, and therefore reduces the time taken for the reaction to reach its endpoint.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 5.0 g sample of an organic compound, containing only carbon and hydrogen, is completely combusted in excess oxygen. The resulting carbon dioxide and water are collected, and their masses are found to be 14.0 g CO₂ and 9.0 g H₂O. What is the empirical formula of the compound?\u003Cbr>(A) C₃H₄\u003Cbr>C₅H₁₀\u003Cbr>C₄H₆\u003Cbr>C₆H₈
सही उत्तर: क) C₃H₄
First, calculate the number of moles of each product: m(CO₂) = 14.0g / 44.0 g/mol = 0.318 mol; m(H₂O) = 9.0g / 18.0 g/mol = 0.500 mol. The ratio of C:H is obtained by dividing the moles of carbon and hydrogen by their lowest common multiple, which simplifies to C₃H₄.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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