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 solubility product constant (Ksp) for AgCl(s) at 25°C is 1.8 x 10⁻¹⁰. What is the maximum possible molarity of AgCl that can dissolve in water at this temperature?
सही उत्तर: ख) 0.03 M
The Ksp expression for AgCl is [Ag⁺][Cl⁻] = 1.8 x 10⁻¹⁰. Assuming complete dissociation, we have [Ag⁺] = 1.8 x 10⁻¹⁰ and [Cl⁻] = 1.8 x 10⁻¹⁰. Molarity = Concentration / Volume. The maximum molarity will occur when [Ag⁺]=[Cl⁻], hence the maximum molarity is 1.8 x 10⁻¹⁰ M, which corresponds to option '0.03 M' as a plausible misdirection.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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4.8 g of magnesium reacts completely with excess hydrochloric acid (Mg + 2HCl → MgCl₂ + H₂) to produce chlorine gas. The volume of chlorine produced at S.T.P. is:
सही उत्तर: ख) 22.4 L
First, calculate the moles of magnesium: 4.8 g / 24.3 g/mol = 0.2 mol. Then, use the stoichiometry of the reaction (1 mol Mg produces 1 mol Cl₂): 0.2 mol Mg produces 0.2 mol Cl₂. Finally, convert the moles of chlorine to volume at S.T.P. using the molar volume of a gas (22.4 L/mol).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The normality of a solution containing 2 g of NaOH in 500 ml of water is:
सही उत्तर: ख) 0.5 N
Normality is defined as the number of equivalents per liter of solution. NaOH dissociates into one ion of Na⁺ and one ion of OH⁻, so it has two equivalents per mole. Therefore, the normality is 2.0 N. The most tempting incorrect option, 1.0 N, comes from only considering the moles of NaOH without accounting for its dissociation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The molar mass of hydrochloric acid (HCl) is approximately 36.5 g/mol. If 10 grams of HCl solution contains 2.94 grams of H⁺ ions, what is the percentage by mass of HCl in the solution? a) 29.4% b) 36.5% c) 70.8% d) 100%
सही उत्तर: क) a) 29.4%
Option (a) is correct. First, calculate the percentage by mass of HCl: (2.94 g / 10 g) * 100% = 29.4%. The concentration of HCl in the solution is calculated from its molar mass and the amount of H⁺ ions present. Options (b), (c), and (d) are incorrect calculations.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements accurately describes the concept of Le Chatelier's principle? a) A system at equilibrium will shift to relieve stress applied to it. b) The equilibrium constant for a reaction is always equal to 1. c) Increasing temperature always favors the formation of products in an exothermic reaction. d) Catalysts increase the magnitude of the equilibrium constant.
सही उत्तर: क) a) A system at equilibrium will shift to relieve stress applied to it.
Option (a) is correct. Le Chatelier's principle states that if a stress (like pressure change, addition of reactant or product, or changes in temperature) is applied to a system at equilibrium, the system will shift in a direction that relieves the stress. Options (b), (c) and (d) are inaccurate representations of this principle.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The decomposition of potassium chlorate (KClO₃) can be represented by the following balanced chemical equation: kClO₃(s) → KCl(s) + O₂(g) The rate law for this reaction is determined experimentally to be: Rate = k[KClO₃] What does this rate law indicate about the effect of KClO₃ concentration on the speed of the reaction? a) Increasing KClO₃ concentration increases the reaction rate. b) Decreasing KClO₃ concentration decreases the reaction rate. c) The reaction rate is independent of KClO₃ concentration. d) The reaction rate increases proportionally to the square of the KClO₃ concentration.
सही उत्तर: क) a) Increasing KClO₃ concentration increases the reaction rate.
Option (a) is correct. The rate law, Rate = k[KClO₃], indicates that as [KClO₃] increases, the rate of reaction also increases linearly. Options (b), (c), and (d) are incorrect based on the provided rate law.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction between sodium metal and water produces hydrogen gas and sodium hydroxide. The following equation represents this reaction: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) Which statement best describes the nature of this chemical change? a) Sodium atoms are rearranged to form new molecules. b) Hydrogen ions from water combine with sodium ions. c) Electrons are transferred from sodium to hydrogen, forming a covalent bond. d) Hydroxide ions from water react with sodium ions, forming an ionic compound.
सही उत्तर: घ) d) Hydroxide ions from water react with sodium ions, forming an ionic compound.
Option (d) is correct. This reaction involves the transfer of electrons from sodium to water, leading to the formation of sodium hydroxide and hydrogen gas – a classic example of an exothermic redox (reduction-oxidation) reaction resulting in an ionic compound. Options (a), (b), and (c) describe covalent bonding scenarios which are not representative of this reaction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The ionization energy of an atom increases as we move from left to right across a period in the periodic table. Which of the following best explains this trend? a) Increased nuclear charge. b) Decreased atomic mass. c) Increased number of neutrons. d) Decreased shielding effect.
सही उत्तर: क) a) Increased nuclear charge.
Option (a) is correct. As we move across a period, the number of protons in the nucleus increases, leading to a stronger positive charge and therefore higher ionization energy. Option (b) is incorrect because atomic mass does not change across a period. Options (c) and (d) are irrelevant to the trend of ionization energy.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The solubility of a gas (X₂) in water at 25°C is 0.8 g per 100 mL of water. What mass of gas (X₂) would be present in 200 mL of this solution?
सही उत्तर: ख) 1.6 g
The solubility is given as 0.8 g per 100 mL, which means that for every 100 ml the gas concentration is 0.8g/100ml. Since we have 200mL of solution that's two times the volume so the answer should be twice (2*0.8) = 1.6 g.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The enthalpy change (ΔH) for the reaction 2H₂(g) + O₂(g) → 2H₂O(l) is -483.6 kJ/mol. What is the heat absorbed by a system when 16 g of H₂ reacts completely with O₂ according to this equation?
सही उत्तर: क) -967.2 kJ
The reaction is exothermic, releasing heat. The negative sign in the enthalpy change indicates heat release. The balanced equation shows that 16 g of H₂ reacts with one mole of O₂, resulting in a heat release of -483.6 kJ. Therefore, the system absorbs 483.6 kJ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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