रसायन विज्ञान (Chemistry) – Chemistry MCQ
रसायन विज्ञान (Chemistry) – इन्जिनियरिङ प्रवेश
Chemistry · Engineering Entrance – Mathematics, Physics, Chemistry & English · ७२८ प्रश्न
७२८ प्रश्न उपलब्ध। मोड छान्नुहोस्:
रसायन विज्ञान (Chemistry): 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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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)
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An aqueous solution of ammonium chloride (NH₄Cl) is:
सही उत्तर: क) Acidic
NH₄Cl is a salt of a strong acid (HCl) and a weak base (NH₄OH); the NH₄⁺ ion hydrolyses to release H⁺, so the solution is acidic. Sodium carbonate, by contrast, gives a basic solution.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the molar solubility of CaF₂ is s mol/L, its solubility product Ksp is:
सही उत्तर: घ) 4s³
CaF₂ ⇌ Ca²⁺ + 2F⁻ gives Ksp = (s)(2s)² = 4s³. s² applies to a 1 : 1 salt like AgCl.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The solubility of AgCl in water decreases when NaCl is added. This is due to:
सही उत्तर: ग) Common ion effect
The added Cl⁻ ions shift AgCl(s) ⇌ Ag⁺ + Cl⁻ to the left, lowering solubility; this is the common ion effect. Very high Cl⁻ concentrations can form complexes, but that is not the usual explanation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which mixture acts as an acidic buffer?
सही उत्तर: ख) CH₃COOH + CH₃COONa
An acidic buffer is a weak acid with its salt of a strong base, like acetic acid and sodium acetate. NH₄OH + NH₄Cl is a basic buffer; HCl + NaCl contains a strong acid and cannot buffer.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The conjugate base of HSO₄⁻ is:
सही उत्तर: घ) SO₄²⁻
A conjugate base is formed when an acid loses a proton: HSO₄⁻ − H⁺ → SO₄²⁻. H₂SO₄ is the conjugate acid of HSO₄⁻.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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