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 following represents an endothermic process:
सही उत्तर: घ) Condensation of water vapor
Endothermic reactions absorb heat from the surroundings, leading to a temperature increase. The rusting of iron is an example as it requires energy input. Combustion and condensation are exothermic processes releasing heat.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The molar mass of glucose (C₆H₁₂O₆) is approximately 180 g/mol. What is the mass (in grams) of oxygen present in 36 g of glucose?
सही उत्तर: ख) 36
The balanced equation for the combustion of glucose is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. We can calculate the mass of oxygen by using stoichiometry. The molar ratio between glucose and oxygen is 1:6. Therefore, in 36g of glucose (6 moles), 6 * 6 = 36 g of oxygen is produced. The other options represent incorrect calculations or assumptions about the reaction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the percentage yield of carbon dioxide gas when 4.4 g of ethanol (C₂H₅OH) are completely oxidized according to the following equation? C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
सही उत्तर: ख) 83%
The balanced equation shows that 1 mole of ethanol produces 2 moles of carbon dioxide. The molar mass of ethanol is 46 g/mol and of CO₂ is 44 g/mol. Therefore, 4.4g / 44 g/mol = 0.1 mole of CO₂ is produced. The percentage yield is (0.1 * 100) / (theoretical yield). The tempting incorrect options relate to other oxidation products or incorrect calculations regarding the stoichiometric ratios.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the primary function of enzymes in biochemical reactions?
सही उत्तर: ख) Decrease activation energy
Enzymes catalyze biochemical reactions by lowering the activation energy required for the reaction to occur. They do not change the equilibrium position of the reaction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which reagent is used to test for the presence of proteins in a solution?
सही उत्तर: ग) Biuret Reagent
The Biuret reagent (a mixture of potassium hydroxide and copper sulfate) reacts with peptide bonds in proteins, forming a violet-colored complex which indicates the presence of protein. Sodium chloride tests for chlorides and copper sulfate is used to test for sulfates.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What does the term 'pH' measure?
सही उत्तर: ख) Concentration of hydrogen ions in a solution
pH stands for ‘potential of Hydrogen’ and measures the concentration of hydrogen ions (H⁺) in an aqueous solution. A lower pH indicates a higher concentration of H⁺ ions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Stainless steel's resistance to rusting stems from the presence of which element(s)?
सही उत्तर: ख) Chromium and nickel
The addition of chromium to iron in stainless steel creates a passive layer of chromium oxide, preventing further corrosion. Options 2, 3 and 4 list other metals commonly added to alloys.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following best describes the concept of ‘degree of unsaturation’ as measured by the “number of rings plus π-bonds”?
सही उत्तर: क) A measure of a compound's boiling point.
The ‘number of rings plus π-bonds’ (degree of unsaturation) is a calculation used to estimate the relative stability of an unsaturated organic molecule, particularly cyclic ones. The other options describe related but distinct properties or measurements.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A sample of magnesium oxide (MgO) is heated strongly in air. What is the main product formed?
सही उत्तर: ग) Carbon dioxide (CO₂) and Magnesium Oxide (MgO)
Heating magnesium oxide in air results in a reaction with oxygen to form magnesium oxide itself. The other options represent different chemical reactions that might occur under similar heating conditions, but are not the primary outcome when MgO is heated in excess air.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the primary reason for the high boiling point of water (H₂O) compared to hydrogen sulfide (H₂S)?
सही उत्तर: क) Water has stronger intermolecular forces due to hydrogen bonding.
Water’s ability to form strong hydrogen bonds between its molecules leads to significantly higher energy requirements for phase changes (boiling). The other options are incorrect because they do not address the fundamental reason for water's unique properties.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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