रसायन विज्ञान – Chemistry MCQ
रसायन विज्ञान – कृषि/वन प्रवेश
Chemistry · Agriculture, Veterinary & Forestry Entrance · ३९२ प्रश्न
३९२ 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 percentage composition of iron (Fe) in hydrated copper sulphate (CuSO₄·xH₂O) is 12%. The value of x will be:
सही उत्तर: घ) 7
If the percentage of Iron is 12%, this means that 12% of CuSO₄·xH₂O contains Fe. Since Cu has a molar mass of approximately 63.5 g/mol and Fe has a molar mass of approximately 55.8 g/mol, the ratio of Cu to Fe in the hydrated copper sulphate is 63.5:55.8. This simplifies to 1:0.94. Therefore, 12% represents 0.94 moles of Fe per mole of CuSO₄·xH₂O. The percentage composition can be calculated using the molar masses (molar mass of CuSO₄ is roughly 159.6 g/mol). The answer 6 arises from a calculation that requires knowing how to calculate the number of moles based on percentage composition. C4 is incorrect as it does not match this ratio.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A compound has the molecular formula C₃H ₆O₃. What is its empirical formula?
सही उत्तर: ख) C₃H₆O₃
The molecular formula C₃H₆O₃ has a mole ratio of 3:6:3 which simplifies to 1:2:1. Therefore, the empirical formula is CH₂O. The most tempting answer, C₆H₁₂O₆, represents glucose and does not match the given formula. “CH₃O” is an incorrect structural arrangement for this compound.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the primary purpose of adding aluminum sulfate (Al₂(SO₄)₃) to acidic soils in Nepal?
सही उत्तर: ग) To provide a source of phosphate nutrients
Aluminum sulfate reacts with the hydrogen ions present in acidic soils, neutralizing them and thus increasing the pH. The other options describe different functions or chemical reactions that don't relate to the initial question.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What type of bond is primarily responsible for the characteristic shape of water molecules (H₂O)?
सही उत्तर: ख) Covalent Bond
Water molecules have a bent shape due to the covalent bonds between oxygen and hydrogen atoms, which results in an uneven distribution of electron density. Ionic and metallic bonds create different arrangements. Van der Waals forces are weak intermolecular attractions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction of limestone (CaCO₃) with hydrochloric acid (HCl) produces which gaseous product?
सही उत्तर: ख) Carbon Dioxide
Limestone reacts with HCl to produce calcium chloride (CaCl₂), water (H₂O), and carbon dioxide (CO₂). This is a classic acid-base reaction. Option 1 is the correct answer; options 2, 3 and 4 are gases that are not formed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following compounds is primarily used as a refrigerant?
सही उत्तर: घ) Carbon Dioxide
Carbon dioxide (CO₂) is widely used as a refrigerant due to its properties. Methane and butane are gases, and ammonia has specific industrial applications but isn’t commonly used for refrigeration.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The process of rusting of iron is primarily influenced by which chemical element present in the air?
सही उत्तर: क) Oxygen
Rusting of iron involves oxidation, and oxygen is the most common oxidizing agent. Carbon dioxide doesn't directly cause corrosion, nitrogen is not a primary reactant, and hydrogen plays no significant role in this process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A solution has a chloride concentration of 0.05 M. What is the molarity of this solution?
सही उत्तर: क) A. 0.05
The question refers to Chloride concentration, and the question asks about molarity. The definition of Molarity is moles per liter. We are given that the chloride concentration is 0.05M, which is already its molarity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the approximate percentage of carbon present in magnesium carbonate (CaCO₃)?
सही उत्तर: घ) D. 80%
The chemical formula for magnesium carbonate is CaCO₃, which contains one calcium atom (Ca), one carbon atom (C), and three oxygen atoms (O). Since the molar mass of C is approximately 12, and the molar mass of Ca and O are around 40 and 16 respectively, the percentage of Carbon is roughly (1 x 12) / (40 + 16 + 16) * 100 = 72%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The decomposition of nitrogenous compounds in soil is primarily facilitated by which group of microorganisms?
सही उत्तर: क) A. Bacteria that convert ammonia into nitrate
Nitrifation, a crucial process in soil nutrient cycling, relies heavily on specific types of bacteria (primarily *Nitrosomonas* species) which convert ammonia to nitrite then nitrate. Option B is incorrect as fungi are involved in decomposition but not specifically nitrogen fixation; option C involves algal photosynthesis and option D refers to protozoa's role in controlling bacterial populations.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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