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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Which of the following statements regarding the hybridisation of carbon atoms in ethyne (C₂H₂) is most accurate? (a) Each carbon atom has sp³ hybridization. (b) Each carbon atom has sp² hybridization. (c) Each carbon atom has sp hybridization. (d) The carbon atoms exhibit resonance structures.
सही उत्तर: ग) (c) Each carbon atom has sp hybridization.
Ethyne (C₂H₂) contains two triple bonds. Each carbon atom is bonded to three other atoms and one hydrogen atom. This requires sp² hybridization for each carbon atom to form the sigma bond with C-H and C-C. Option (a) is incorrect because sp³ would require four bonds, which doesn't occur in ethyne. Option (c) incorrectly suggests sp hybridization.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Plaster of Paris is used in hospitals for making casts to support fractured bones because, when mixed with water, it undergoes rapid hydration and sets into a hard, rigid mass. Which of the following statements BEST explains this process? (a) It reacts vigorously with bone tissue, promoting healing. (b) It forms a strong adhesive bond with the surrounding skin. (c) It undergoes a chemical reaction with water to produce calcium hydroxide and gypsum. (d) It absorbs moisture from the air, increasing its volume and pressure within the fracture site.
सही उत्तर: ग) (c) It undergoes a chemical reaction with water to produce calcium hydroxide and gypsum.
Plaster of Paris (calcium sulfate hemihydrate - CaSO₄·½H₂O) hydrates when mixed with water to form gypsum (CaSO₄·2H₂O). This is a physical process involving the absorption of water, not a chemical reaction. Option (a) is incorrect as it proposes a damaging reaction. Option (b) is wrong as plaster does not create an adhesive bond. Option (d) is also false because plaster doesn't absorb moisture to increase pressure.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What volume of 0.5 M hydrochloric acid (HCl) is required to completely neutralize 36 grams of magnesium carbonate (MgCO₃)? (Molar mass of MgCO₃ = 84 g/mol)
सही उत्तर: क) 2.0 L
The correct answer (4.0 L) is obtained by calculating the moles of MgCO₃, then using the stoichiometry of the reaction between HCl and MgCO₃ to determine the volume of 0.5 M HCl required for neutralization.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following is NOT a characteristic property of acids?
सही उत्तर: क) Taste sour
The correct answer (Conducts electricity in their aqueous solutions) is incorrect. Acids generally do not conduct electricity well in water, while the other options accurately describe properties of acids – they taste sour, react with carbonates to produce carbon dioxide, and neutralize bases by accepting protons.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction: 2NH₃(g) + O₂(g) → 2NO(g) + H₂O(g) is reversible. If the equilibrium constant Kp for this reaction at a given temperature is 4.5 x 10⁻³, what is the partial pressure of NO in equilibrium with 1 atm NH₃ and 1 atm O₂?
सही उत्तर: क) 1 atm
The correct answer (2.25 atm) is calculated using the expression for Kp: Kp = (P(NO)² * P(H₂O)) / P(NH₃) * P(O₂). The other options incorrectly apply the equilibrium constant or fail to account for the partial pressures of all reactants and products.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The dissociation constant (Ka) for a weak acid HA in water is 1.8 x 10⁻⁵. What is the concentration of HA at equilibrium if initially 0.1 M HA was dissolved in water?
सही उत्तर: क) 0.018 M
The correct answer (0.018 M) is derived from the Ka expression and equilibrium calculations. The other options are incorrect because they either misinterpret the Ka value or fail to account for the initial concentration of the weak acid in establishing the equilibrium.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The standard enthalpy of formation of gaseous ammonia (NH₃) at 298 K is -91.8 kJ/mol. Which of the following statements is true regarding this value?
सही उत्तर: ख) It represents the heat absorbed when 1 mole of NH₃ is formed from its elements in the standard conditions
The standard enthalpy of formation defines the heat change (ΔH°) when one mole of a substance is formed from its elements in their standard states. A negative value indicates heat release (exothermic reaction), which is the case for ammonia formation. The other options misinterpret the meaning of the enthalpy of formation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The following reaction represents a redox process: CH₃COOH + 2N₂O → CO₂ + (CN)₂ + 3H₂O. Which of the following statements accurately describes this reaction?
सही उत्तर: क) Reduction of Nitrous Oxide
In this reaction, nitrous oxide (N₂O) is reduced to cyanamide ((CN)₂) while acetic acid (CH₃COOH) is oxidized. The change in oxidation states confirms the redox process. The other options are incorrect because they do not accurately describe the transformation of reactants and products.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements accurately describes the role of a catalyst in a chemical reaction?
सही उत्तर: ग) c) It speeds up the rate of both forward and reverse reactions without being consumed.
A catalyst accelerates a chemical reaction by lowering its activation energy, thus increasing the rates of both the forward and reverse reactions. This is achieved without being permanently altered itself. Options (a), (b), and (d) are incorrect descriptions of a catalyst's function.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction of ethanol with excess hydrochloric acid produces which of the following products?
सही उत्तर: क) a) Ethanoic acid
Ethanol reacts with concentrated HCl to form chloroethane (chloromethane) and a small amount of ethanol. This is due to the reaction occurring at both ends of the molecule, following Markovnikov’s rule. Option (b) represents a different reaction pathway.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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