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 Haber-Bosch process for ammonia synthesis requires high pressure primarily to influence which aspect of the reaction?
सही उत्तर: ग) Reaction Equilibrium
According to Le Chatelier's principle, increasing the pressure favors the side with fewer gas molecules. The Haber-Bosch process produces ammonia (a gas) and hydrogen (a gas). Increasing the pressure shifts the equilibrium towards ammonia formation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Saponification, a key reaction in soap manufacture, involves which type of chemical change?
सही उत्तर: ग) Hydrolysis
Saponification is the hydrolysis (breakdown with water) of fats and oils. This specifically breaks down the ester bonds present in triglycerides into fatty acids and glycerol – forming soap. The other options represent different chemical reactions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements best describes the primary chemical process involved in the extraction of aluminium from bauxite ore?
सही उत्तर: ग) Reduction with carbon monoxide
The Bayer process utilizes the reduction of alumina (formed from bauxite) by heat and carbon monoxide. Carbon monoxide reacts with aluminum oxide to form aluminum metal and carbon monoxide is reduced to carbon. The other options are used in different metallurgical processes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The rate constant (k) for a second order reaction is inversely proportional to which of the following?
सही उत्तर: क) Time
A second-order reaction's rate constant decreases as the concentration of reactant A increases. The other options – time, temperature, and surface area – do not directly influence the rate constant for a second-order reaction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The decomposition of potassium chlorate (KClO₃) can be represented as: 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g). When this reaction is heated, the solid KClO₃ disappears. Which statement best explains why oxygen gas is produced? (a) Oxygen is a reactant and is consumed during the reaction. (b) Oxygen is a product of the chemical decomposition of KClO₃. (c) Oxygen is released as heat is absorbed by the reaction mixture. (d) Oxygen is created from the mixing of potassium chloride and oxygen gas.
सही उत्तर: ख) (b) Oxygen is a product of the chemical decomposition of KClO₃.
The balanced equation shows that 3 moles of O₂ are produced for every 2 moles of KClO₃ decomposed. Thus, oxygen is a product of this decomposition reaction. Options (a), (c) and (d) are incorrect descriptions of the process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The process of dissolving ammonium chloride (NH₄Cl) in water involves the formation of ions. Which species is primarily responsible for the slight decrease in temperature observed during dissolution? (a) NH₄⁺ (b) Cl⁻ (c) H₂O (d) H₃O⁺
सही उत्तर: ग) (c) H₂O
Dissolution of ammonium chloride is an endothermic process that absorbs heat from the surroundings. The absorption of this heat by water molecules causes a decrease in temperature. Option (a) and (d) are spectators; (b) does not directly contribute to heat change; and (c) is responsible for absorbing the heat.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl) is a classic example of an exothermic neutralization reaction. What is the primary change in energy during this process? (a) Kinetic energy increases significantly. (b) Potential energy of the chemical bonds increases. (c) Thermal energy (heat) is released into the surroundings. (d) The mass of the products exceeds the mass of the reactants.
सही उत्तर: ग) (c) Thermal energy (heat) is released into the surroundings.
The neutralization reaction releases heat due to the formation of water molecules from the hydrogen and hydroxide ions. This represents a decrease in potential energy as bonds are formed. Option (a) describes changes in kinetic energy; (b) describes an increase in potential energy, which is incorrect; and (d) concerns mass conservation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements correctly describes the process of oxidation? (a) Loss of electrons by a substance (b) Gain of oxygen by a substance (c) Gain of electrons by a substance (d) Loss of hydrogen by a substance
सही उत्तर: क) (a) Loss of electrons by a substance
Oxidation is defined as the loss of electrons from an atom, molecule or ion. Option (b), gain of oxygen, represents reduction. Options (c) and (d) are incorrect definitions of oxidation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the main chemical principle behind the action of fertilizers on plants?
सही उत्तर: ग) Fertilizers cause plants to produce their own food from sunlight
Fertilizers primarily deliver essential elements like nitrogen, phosphorus, and potassium – which are macronutrients – to plants. These nutrients are critical for various plant processes including photosynthesis, cell growth, and overall development. Option 1 is incorrect as fertilizers don't directly stimulate cell division; option 3 is wrong because plants produce their own food through photosynthesis; and option 4 describes transpiration.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The reaction between hydrochloric acid (HCl) and sodium carbonate (Na₂CO₃) produces carbon dioxide gas. What is the balanced chemical equation for this reaction?
सही उत्तर: ग) HCl + NaHCO₃ → NaCl + H₂O + CO₂
The reaction between HCl and Na₂CO₃ results in the formation of sodium chloride (NaCl), water (H₂O), and carbon dioxide (CO₂). Balancing the equation ensures that the number of atoms of each element is equal on both sides. Option 1 does not balance correctly and options 3 & 4 are incorrect as they involve different reactants.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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