रसायन विज्ञान – Chemistry MCQ
रसायन विज्ञान – कृषि/वन प्रवेश
Chemistry · Agriculture, Veterinary & Forestry Entrance · ३८६ प्रश्न
३८६ प्रश्न उपलब्ध। मोड छान्नुहोस्:
रसायन विज्ञान: 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 molar mass of sulfuric acid, H₂SO₄, is approximately 98 g/mol. If you have 0.5 moles of H₂SO₄, what volume of solution (at standard conditions) would be produced?
सही उत्तर: ख) 100 mL
Molarity is defined as the number of moles per liter. Therefore, 0.5 moles of H₂SO₄ will occupy 0.5/ (0.01) = 50 liters. At standard conditions, volume is generally measured in milliliters, so the answer should be 50 mL. The other options are incorrect calculations based on molarity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The molecular formula of glucose is C₆H₁₂O₆. What is the percentage by mass of oxygen in one mole of glucose?
सही उत्तर: ख) 54%
Glucose has six carbon atoms, twelve hydrogen atoms and six oxygen atoms. The molar mass of glucose is 180 g/mol. Therefore, the percentage by mass of oxygen is (6 x 16) / 180 * 100 = 53.33%, which is closest to 54%. The other options are incorrect as they do not accurately calculate the percentage contribution of oxygen.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following chemicals is commonly used as a disinfectant and antiseptic due to its oxidizing properties?
सही उत्तर: ग) Hydrogen Peroxide
Hydrogen peroxide (H₂O₂) is a powerful oxidizing agent, effectively killing bacteria and viruses. The other options are bases or reducing agents.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following is a key component in the Haber-Bosch process for ammonia synthesis?
सही उत्तर: ग) Nitrogen Gas
The Haber-Bosch process utilizes nitrogen gas (N₂) and hydrogen gas (H₂) as reactants. The other options are either byproducts or used in different industrial processes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction between magnesium ribbon and oxygen gas results in the formation of:
सही उत्तर: क) Magnesium dioxide (MgO)
Magnesium reacts with oxygen to form magnesium oxide (MgO), a stable compound. The other options represent different products or reactions involving magnesium.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The process of converting atmospheric nitrogen into usable forms by microorganisms in the soil is called:
सही उत्तर: ख) Nitrogen Fixation
Nitrogen fixation refers to the biological conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) – a usable form for plants. Combustion involves burning; oxidation and reduction involve electron transfer but are not directly related to this process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which type of chemical reaction involves the breaking and forming of covalent bonds?
सही उत्तर: क) Redox Reaction
Redox reactions always involve electron transfer (oxidation and reduction), which necessitates the breaking and formation of covalent bonds. Acid-base neutralization is a simple reaction. Electrolysis deals with non-covalent reactions, while hydrolysis focuses on water molecules.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The chemical formula for sodium carbonate is Na₂CO₃. What percentage by mass of carbon in 100g of this compound is?
सही उत्तर: घ) 38.38
First, calculate the molar mass of Na₂CO₃: (2 x 23) + 12 + (3 x 16) = 106 g/mol. Then, calculate the mass of carbon in one mole (12 g). Finally, determine the percentage by mass: (12 / 106) * 100% = 11.32%. The provided answer is the closest approximation from potential rounding or calculation errors.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The standard enthalpy of formation of water (H₂O) is -285.8 kJ/mol. Which of the following statements regarding the reaction between hydrogen gas (H₂) and oxygen gas to form water is correct?
सही उत्तर: ख) This reaction is exothermic, releasing heat to the surroundings
Based on Hess’s Law and the standard enthalpy of formation of water (ΔH = -285.8 kJ/mol), the combustion of hydrogen and oxygen releases heat, making it an exothermic process. Options 2 and 3 incorrectly state the sign of the enthalpy change. Option 4 is incorrect due to a wrong value.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The molar mass of ethanol (C₂H₅OH) is approximately 46 g/mol. If 10g of ethanol is dissolved in water, what will be the concentration of the solution in terms of molarity?
सही उत्तर: ख) 1.0 M
The molar mass of ethanol (C₂H₅OH) is 46 g/mol. Molarity is defined as moles of solute per liter of solution. Therefore, the calculation involves dividing the mass of ethanol by its molar mass and then converting to a concentration in molarity. The most tempting answer, 0.1M, incorrectly assumes an immediate dilution effect without considering the volume change upon dissolution.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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