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 lanthanide contraction is primarily attributed to:\u003Cbr>(A) Similar size of 4f orbitals\u003Cbr>Radius dependence of screening effect\u003Cbr>Similar electronegativity values\u003Cbr>Increased nuclear charge
सही उत्तर: क) Similar size of 4f orbitals
The lanthanide contraction is the observed decrease in atomic radii within the lanthanide series. This occurs due to the poor shielding effect of the partially filled 4f orbitals—the electrons are not effectively shielded from the nucleus leading to a smaller measured radius and this size shrinkage affects the physical properties.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following processes is most effective for separating a mixture of ferrous oxide and haematite ores?\u003Cbr>(A) Magnetic separation\u003Cbr>Selectively acidic leaching\u003Cbr>Bubble AGM flotation\u003Cbr>Liquid-liquid extraction
सही उत्तर: क) Magnetic separation
The froth flotation method utilizes differences in the surface properties of minerals. Ferrous oxide (iron oxides) are hydrophobic and will attach to air bubbles, allowing them to float to the top during agitation whereas haematite is hydrophilic and remains at the bottom. Magnetic separation relies on magnetic susceptibility, which isn't a primary factor here.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The root mean square (rms) velocity of gas molecules is directly proportional to which of the following?\u003Cbr>(A) Pressure\u003Cbr>Number\u003Cbr>Radius\u003Cbr>Surface area
सही उत्तर: क) Pressure
The root mean square velocity (v_rms) is calculated as v_rms = √(3RT/M), where R is the ideal gas constant, T is the absolute temperature, and M is the molar mass. The formula shows that v_rms is directly proportional to the square root of the temperature (T) and inversely proportional to the square root of the molar mass (M). Since pressure is related to temperature through the Ideal Gas Law (PV=nRT), pressure is indirectly proportional to v_rms.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 2.0 M solution of sodium chloride (NaCl) is prepared by dissolving 4.3 g of NaCl in water. What is the molarity of the solution in mol/L?
सही उत्तर: क) 1.0 M
The problem involves calculating the molarity of a given concentration. The formula for molarity (M) is moles of solute / liters of solution. We are given 4.3 g of NaCl, and its molecular weight is approximately 58.44 g/mol. So, moles = 4.3 g / 58.44 g/mol ≈ 0.0736 mol. The volume of the solution is calculated from the molarity: Volume = moles / Molarity = 0.0736 mol / 2.0 M = 0.0368 L = 36.8 mL. The correct answer is 2.0 M because it aligns with the calculations and reflects the dilution process. The other options are incorrect as they don't accurately reflect the moles calculated from the given mass of NaCl.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The hydrolysis of which of the following compounds would produce a basic solution?
सही उत्तर: ग) (CH₃)₂NH
Hydrolysis refers to the reaction with water. Carboxylic acids (like CH₃CH₂COOH) are weak acids and upon hydrolysis, they produce H⁺ ions which results in a basic solution. The other options, like CH₃COONa and (CH₃)₂NH, do not generate hydroxide ions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements correctly describes the effect of increasing the concentration of a catalyst in a reversible reaction?
सही उत्तर: ग) The rate of the forward reaction increases
Increasing the concentration of a catalyst shifts the equilibrium towards the product side according to Le Chatelier's principle. This happens because the catalyst participates in both the forward and reverse reactions, effectively speeding up the process of converting reactants into products, however it does not change the equilibrium constant itself.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction: N₂O₄ → 2NO₂ takes place in a closed container at constant volume. At equilibrium, the partial pressure of NO₂ is 400 torr. What is the partial pressure of N₂O₄ at this equilibrium?
सही उत्तर: घ) 400 torr
According to Le Chatelier's principle, changes in volume will not affect the equilibrium constant for a reaction at constant volume. The ratio of partial pressures for N₂O₄ and NO₂ at equilibrium is always 2:1. Therefore, if [NO2] = 400 torr, then [N2O4] = 200 torr.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The molar solubility of silver chloride (AgCl) in water at 25°C is 1.93 x 10⁻³ M. Ksp for AgCl is:
सही उत्तर: क) 1.93 x 10⁻³
The solubility product constant (Ksp) for AgCl is [Ag⁺][Cl⁻] = 1.93 x 10⁻³ M. Since the concentration of Ag⁺ is equal to its molar solubility, we have [Ag⁺] = 1.93 x 10⁻³ M. Therefore, [Cl⁻] must also be 1.93 x 10⁻³ M. The most tempting option, 3.94 x 10⁻¹⁰, is incorrect because it represents a significantly smaller value than the calculated concentration of chloride ions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the oxidation state of chromium (Cr) in the compound Cr₂O₇?
सही उत्तर: घ) +4
In Cr₂O₇, each Cr atom has a +6 oxidation state. This is determined by balancing the oxygen atoms with the correct chromium charge. The other options represent different possible oxidation states of chromium in various compounds.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements accurately describes the reaction between ethanol and hydrochloric acid (HCl)?
सही उत्तर: ग) The reaction produces primarily chloroform due to Markovnikov's rule.
The reaction between ethanol and HCl follows Markovnikov’s rule, leading to the formation of chloroethane (the major product). This is an SN1 mechanism which results in racemization - i.e., inversion of configuration at the chiral carbon. Options 1 & 4 are incorrect because they describe different reaction pathways and products. Option 3 is wrong as it describes an alternative, less likely outcome.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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