इन्जिनियरिङ प्रवेश – Mathematics, Physics, Chemistry, English
इन्जिनियरिङ प्रवेश – Mathematics, Physics, Chemistry, English
Engineering Entrance – Mathematics, Physics, Chemistry & English · ३,८४१ प्रश्न
३,८४१ प्रश्न उपलब्ध। मोड छान्नुहोस्:
इन्जिनियरिङ प्रवेश: 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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A catalyst increases the rate of a reaction by:
सही उत्तर: ग) Lowering the activation energy
A catalyst provides an alternative pathway with lower activation energy. It speeds up forward and backward reactions equally, so it does not change the position of equilibrium.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a first-order reaction with rate constant k = 0.0693 min⁻¹, the half-life is:
सही उत्तर: ख) 10 min
For first-order kinetics t½ = 0.693/k = 0.693/0.0693 = 10 min. Note that t½ is independent of initial concentration for first-order reactions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The oxidation number of oxygen in hydrogen peroxide (H₂O₂) is:
सही उत्तर: क) −1
In H₂O₂: 2(+1) + 2x = 0, so x = −1, as in all peroxides. −2 is the usual oxidation state of oxygen in oxides.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The oxidation number of sulphur in sodium thiosulphate (Na₂S₂O₃) is (average):
सही उत्तर: घ) +2
2(+1) + 2x + 3(−2) = 0 gives x = +2 (average over both S atoms). +6 is the oxidation state of S in Na₂SO₄.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a galvanic (voltaic) cell, the anode is:
सही उत्तर: ग) Negative electrode where oxidation occurs
In a galvanic cell oxidation at the anode releases electrons, making it the negative terminal. In an electrolytic cell the anode is positive, which is a common source of confusion.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which metal is the strongest reducing agent in aqueous solution?
सही उत्तर: ख) Li
Lithium has the most negative standard reduction potential (about −3.04 V), so it loses electrons most readily in water. Silver, with a positive potential, is a poor reducing agent.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In an electrolytic cell, the cathode is the electrode where:
सही उत्तर: क) Reduction takes place
In all cells reduction occurs at the cathode; in electrolysis cations move to the cathode and gain electrons. Anions are discharged by oxidation at the anode.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The quantity of electricity needed to deposit 1 mol of copper from a Cu²⁺ solution is:
सही उत्तर: घ) 2 faradays (≈ 193,000 C)
Cu²⁺ + 2e⁻ → Cu needs 2 mol of electrons per mole of Cu, i.e. 2 F ≈ 193,000 C. One faraday would deposit only half a mole of copper.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The oxidation number of manganese in KMnO₄ is:
सही उत्तर: ग) +7
With K = +1 and four O at −2: 1 + x − 8 = 0, so x = +7. +6 is the oxidation state of Mn in K₂MnO₄ (manganate).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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50 mL of 0.1 M HCl is mixed with 50 mL of 0.1 M NaOH at 25 °C. The pH of the resulting solution is:
सही उत्तर: ख) 7
Both contain 5 mmol, so the strong acid and strong base exactly neutralise to give NaCl, which does not hydrolyse; pH = 7. A pH of 1 would require excess acid at 0.1 M.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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