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 compounds will exhibit the largest positive value for its enthalpy of formation (ΔHf)?
सही उत्तर: घ) C₆H₁₂O₆(s)
The enthalpy of formation is negative for compounds formed from simpler elements. Water (H₂O) has the largest positive value for its ΔHf because it's formed from two highly electronegative elements (oxygen and hydrogen). The other options are hydrocarbons or carbohydrates which are generally more stable and have a smaller (more negative) ΔHf.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The decomposition of hydrogen peroxide (H₂O₂) catalyzed by manganese dioxide (MnO₂) produces oxygen gas and water. Which statement best explains why MnO₂ is used as a catalyst?
सही उत्तर: ग) It increases the concentration of H₂O₂ in solution.
A catalyst works by lowering the activation energy required for a chemical reaction to occur. MnO₂ provides an alternative pathway with a lower energy barrier, speeding up the decomposition without being consumed itself. The other options describe incorrect mechanisms of catalysis.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction between sodium hydroxide (NaOH) and carbon dioxide (CO₂) produces a weak acid. What is the primary chemical species responsible for this acidification?
सही उत्तर: घ) Hydroxide ion (OH⁻)
The reaction between NaOH and CO₂ produces sodium bicarbonate (NaHCO₃). This compound is an unstable salt that readily decomposes in water to form carbonic acid (H₂CO₃), a weak acid. The other options are stable salts and do not contribute to acidification.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The coordination number of chromium(III) ion in [Cr(H₂O)₆]³⁻ is?
सही उत्तर: ख) 6
The coordination number refers to the number of ligands directly attached to a central metal atom. In [Cr(H₂O)₆]³⁻, six water molecules coordinate to the chromium ion, therefore giving it a coordination number of 6.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the concentration of a solution prepared by dissolving 2g of sodium carbonate (Na₂CO₃) in water and diluting to a final volume of 250mL? (Molar mass of Na₂CO₃ = 106 g/mol).
सही उत्तर: ख) 0.02 M
First, calculate the moles of Na₂CO₃: 2g / 106g/mol = 0.019 mol. Then, divide by the volume in liters: 0.019 mol / 0.25 L = 0.076 M which is closest to 0.08 M.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Consider the reaction: N₂O₄(g) → 2NO₂(g). If the standard enthalpy change for this reaction is -1.5 kJ/mol, what is the heat absorbed or released when 3 moles of N₂O₄ decompose?
सही उत्तर: क) -4.5 kJ
The enthalpy change is given per mole. Therefore, for 3 moles, we multiply the value by 3: -1.5 kJ/mol * 3 mol = -4.5 kJ. This indicates heat absorbed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The molar mass of glucose (C₆H₁₂O₆) is approximately 180 g/mol. If 36g of glucose is dissolved in water to make 200mL solution, what will be the approximate molarity of this solution?
सही उत्तर: ख) 1.0 M
First calculate the moles of glucose: 36g / 180 g/mol = 0.2 mol. Then, divide the number of moles by the volume in liters: 0.2 mol / 0.2 L = 1.0 M. The other options result from incorrect calculations or approximations.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements accurately describes Le Chatelier's Principle?
सही उत्तर: ग) The rate of a reaction will increase if a catalyst is added
Le Chatelier's Principle states that when a change of condition (stress) is applied to a system at equilibrium, the system will shift in a direction that relieves the stress. The other options are incorrect descriptions or misconceptions about equilibrium.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The molar mass of potassium permanganate (KMnO₄) is approximately:
सही उत्तर: ख) 132 g/mol
Potassium (K) has a molar mass of 39.1 g/mol, manganese (Mn) is 54.9 g/mol and oxygen (O) is 16.0 g/mol. Therefore, K + Mn + 4O = 39.1 + 54.9 + (4 * 16.0) = 196 g/mol.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The percentage composition of carbon in magnesium carbonate (MgCO₃) is 40%. What is its empirical formula?
सही उत्तर: घ) Mg₂(CO₃)₃
Magnesium carbonate contains one atom of carbon and three atoms of oxygen. The percentage composition given indicates that for every 100g of the compound, 40g is carbon. This corresponds to Mg(CO₃)₂ based on the ratio of mass. The other options have incorrect ratios of elements.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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