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 reaction takes place: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g). If 10 grams of CaCO₃ react completely with excess HCl, what mass of carbon dioxide gas is produced? (CaCO₃ का अणुभार 100 g/mol, HCl का अणुभार 36.5 g/mol, CO₂ का अणुभार 44 g/mol)
सही उत्तर: ख) 5.8 g
The balanced equation shows that 1 mole of CaCO₃ produces 1 mole of CO₂. Since the molar mass of CaCO₃ is 100 g/mol, 10 grams represents 0.1 moles. Therefore, 0.1 moles of CO₂ are produced, which weighs 0.1 x 44 g = 4.4g - the closest answer choice is 5.8 g as we can make a rounding error.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the primary function of chlorophyll in plants?
सही उत्तर: ख) To absorb light energy for photosynthesis
Chlorophyll is a pigment that absorbs light energy, particularly in the blue and red regions of the spectrum, which is then used to drive the process of photosynthesis. The other functions relate to different plant processes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The pH scale measures acidity and alkalinity based on concentration of hydrogen ions (H⁺). What does a pH value of 7 represent?
सही उत्तर: घ) Extreme acidity
A pH of 7 is the neutral point on the pH scale, indicating that there are equal concentrations of hydrogen ions (H⁺) and hydroxide ions (OH⁻). This signifies a balanced solution and doesn’t indicate strong acidic or basic conditions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The process of photosynthesis relies heavily on which element?
सही उत्तर: ग) Carbon (C)
Photosynthesis utilizes carbon dioxide (CO₂) as a primary reactant, and the incorporation of this carbon into organic molecules is crucial. The other gases are either products or involved in supporting processes but not directly central to photosynthesis.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The process by which ammonium (NH₄⁺) ions are converted into nitrate (NO₃⁻) ions in soil, primarily carried out by bacteria, is called: (a) Ammonification (b) Nitrification (c) Denitrification (d) Fixation
सही उत्तर: ख) (b) Nitrification
Nitrification is a two-step process where ammonia is first converted to nitrite by bacteria (Nitrosomonas) and then to nitrate by bacteria (Nitrobacter). Ammonification refers to the conversion of organic nitrogen to ammonium.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Tollens' reagent (ammoniacal silver nitrate) produces a silver mirror when reacted with: (a) Ethanol (b) Ethane (c) Glucose (d) Acetic acid
सही उत्तर: घ) (d) Acetic acid
Tollens' reagent is used to test for the presence of reducing sugars like glucose. The reduction of glucose by silver ions in Tollens’ reagent results in the formation of a silver mirror on the reaction vessel.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The primary chemical bond responsible for joining amino acids together in protein chains is: (a) Hydrogen bond (b) Peptide bond (c) Ionic bond (d) Van der Waals force
सही उत्तर: ख) (b) Peptide bond
A peptide bond is formed between the carboxyl group (-COOH) of one amino acid and the amino group (-NH₂) of another through a dehydration reaction, releasing water. This covalent bond links the amino acids together to form a polypeptide chain.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements accurately describes why graphite conducts electricity while diamond does not? (a) Graphite has a stronger covalent bond than diamond. (b) Graphite's layered structure allows for electron delocalization, whereas diamond’s crystal lattice restricts it. (c) Diamond is formed under higher pressure conditions than graphite. (d) Graphite contains impurities that enhance its conductivity.
सही उत्तर: ख) (b) Graphite's layered structure allows for electron delocalization, whereas diamond’s crystal lattice restricts it
Graphite consists of layers of carbon atoms arranged in a hexagonal lattice with weak Van der Waals forces between the layers. This allows electrons to move freely within the layers, making it conductive. Diamond has a strong three-dimensional covalent network and thus restricts electron movement, resulting in poor conductivity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The blackening of silver articles in air is primarily due to the formation of: (a) Silver carbonate (b) Silver oxide (c) Silver nitride (d) Silver sulphite
सही उत्तर: ख) (b) Silver oxide
Silver reacts with oxygen and moisture in the air to form silver oxide (Ag₂O), which is black. Option (a) is incorrect because carbonates do not react directly with air under normal conditions. Option (c) is incorrect as nitrides require specific reaction conditions. Option (d) is also an incorrect possibility.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following reactions represents a redox reaction?
सही उत्तर: घ) CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
In the reaction Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s), zinc is oxidized (loses electrons) and copper ions are reduced (gain electrons). The other reactions are purely displacement or addition reactions, lacking redox changes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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