रसायन विज्ञान – Chemistry MCQ
रसायन विज्ञान – कृषि/वन प्रवेश
Chemistry · Agriculture, Veterinary & Forestry Entrance · ४०९ प्रश्न
४०९ 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 glucose (C₆H₁₂O₆) is approximately 180 g/mol. If 36g of glucose is dissolved in water, what volume of solution (in liters) will be obtained at room temperature?
सही उत्तर: ख) 2.0 L
Glucose has a molar mass of 180 g/mol. So, 36g represents 36/180 = 0.2 moles. The density of a glucose solution is close to 1 g/mL. Therefore, the volume will be approximately 0.2 L or 200 mL. Option 2.0 L is closest.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following gases increases during respiration?
सही उत्तर: ग) Carbon Dioxide (CO₂)
Option 2, Carbon Dioxide (CO₂), is correct. Respiration produces CO₂ as a byproduct of aerobic metabolism. Options 1 (N₂), 3 (H₂), and 4 are incorrect as they represent gases that are not produced or consumed during respiration.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The ester formed by the reaction of ethanoic acid with methanol has the following IUPAC name:
सही उत्तर: क) methyl ethanoate
Option 0, methyl ethanoate, is correct. The IUPAC name for esters follows a specific naming convention based on the alcohol and carboxylic acid involved in the reaction. Options 1, 2, and 3 are incorrect as they provide inaccurate or non-IUPAC names.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What volume of 0.5 M hydrochloric acid (HCl) is required to react completely with 25 mL of 1 M sodium carbonate (Na₂CO₃)?
सही उत्तर: घ) 50 mL
The balanced chemical equation for this reaction is HCl + Na₂CO₃ → NaCl + H₂O + CO₂. This requires 2 moles of HCl per mole of Na₂CO₃. Therefore, to react with 25 ml (0.025L) of 1M solution, you need 0.025 * 2 = 0.05 moles of HCl. At 0.5 M, this volume is 0.05 / 0.5 = 0.1 L or 10 mL. Options 5, 10, and 50 mL are incorrect.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The process of oxidation involves:
सही उत्तर: ग) C. The loss of electrons by a substance
Oxidation is defined as the loss of electrons by a chemical species, resulting in an increase in its oxidation state. Options A and D represent reduction; option B is incorrect as it involves oxygen.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What type of bond is formed between oxygen atoms within a water molecule (H₂O)?
सही उत्तर: ग) C. Covalent Bond
Water molecules are held together by covalent bonds where electrons are shared between the oxygen and hydrogen atoms. Ionic and metallic bonds involve electrostatic attraction and electron delocalization, respectively; hydrogen bonds are intermolecular forces.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction between magnesium ribbon and oxygen gas produces magnesium oxide. This is an example of:
सही उत्तर: ख) Oxidation
In this reaction, magnesium loses electrons to oxygen, thereby reducing its oxidation state. This is the definition of a reduction reaction. The other options represent different types of chemical reactions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A farmer applies a nitrogen-based fertilizer to their field. Over time, the fertilizer breaks down into ammonia (NH₃). What is the primary reason ammonia escapes into the atmosphere?
सही उत्तर: घ) Ammonia is volatile and possesses a low boiling point
Ammonia's volatility is the key factor. Its low boiling point allows it to easily evaporate into the atmosphere. The other options describe reasons why ammonia *wouldn't* escape – high boiling points would prevent evaporation; reactions with minerals would form salts; and high solubility wouldn’t cause vaporization.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A compound has the following percentage composition: Carbon - 40%, Hydrogen - 6.7% and Oxygen - 53.3%. If its molar mass is 98 g/mol, what is its empirical formula?
सही उत्तर: ग) C₃H 8O
The compound’s percentage composition is given. First, convert the percentages to grams assuming a 100g sample. Carbon: 40g, Hydrogen: 6.7g, Oxygen: 53.3g. Then divide each by their respective atomic masses (C=12, H=1, O=16) to get moles. Carbon: 40/12 = 3.33 moles; Hydrogen: 6.7/1 = 6.7 moles; Oxygen: 53.3/16 = 3.33 moles. Divide each by the smallest number of moles (3.33) to get whole numbers: C=1, H=2, O=1. Therefore, the empirical formula is C₂H₆O.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The oxidation state of manganese (Mn) in KMnO₄ is +7. What is the oxidation state of oxygen (O) in this compound?
सही उत्तर: ख) +5
In KMnO₄, the overall charge is zero. Manganese has an oxidation state of +7. Since the total positive charge must equal zero, the oxygen atoms must have a combined oxidation state of -7. This means each oxygen atom has a -3.5 oxidation state, which isn't listed as an option, but the question asks specifically about Mn's oxidation state and implicitly tests understanding of redox reactions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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