रसायन विज्ञान – Chemistry MCQ
रसायन विज्ञान – IT प्रवेश
Chemistry · IT Entrance – B.Sc. CSIT, BIT & BCA · ६४१ प्रश्न
६४१ 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 pH of a solution is 7. What can be concluded about the concentration of hydrogen ions (H⁺) in this solution? (pH 7 को घोलिमा हाइड्रोजन आयन (H⁺) को सांद्रता बारे निम्न प्रश्न सोधिएको छ: What conclusions can be drawn about the concentration of hydrogen ions (H⁺) in a solution with pH 7?)
सही उत्तर: ग) The concentration of H⁺ is equal to that of OH⁻.
pH is a measure of acidity and alkalinity, defined as the negative logarithm of hydrogen ion concentration ([H+]). A pH of 7 indicates neutrality, where [H⁺] = [OH⁻].
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following statements accurately describes Avogadro's Law? (अघاديको नियम बुझाइ गरी निम्न प्रश्न सोधिएको छ: Which of the following statements accurately describes Avogadro's Law?)
सही उत्तर: क) Equal volumes of gases always contain equal numbers of molecules.
Avogadro's Law states that equal volumes of gases under the same conditions of temperature and pressure contain an equal number of moles (and therefore molecules).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The following reaction takes place: CH₃COOH + NaOH → ? This reaction demonstrates which fundamental principle in chemistry? (एसिड-बेस प्रतिक्रियाको आधारमा निम्न प्रश्न सोधिएको छ: CH₃COOH + NaOH → ?)
सही उत्तर: क) Acid neutralization
The reaction of a carboxylic acid (CH₃COOH) with sodium hydroxide (NaOH) results in the formation of a salt and water. This is the fundamental principle of acid-base neutralization – where an acid reacts with a base to form a new compound and water. The other options represent different types of chemical reactions that do not align with this specific process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Chlorobenzene is converted into phenol (Dow's process) by heating it with:
सही उत्तर: घ) aqueous NaOH at about 623 K and high pressure, followed by acidification
The C–Cl bond in chlorobenzene is strong (partial double-bond character), so drastic conditions are needed to form sodium phenoxide, which acid converts to phenol.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Benzene reacts with acetyl chloride in the presence of anhydrous AlCl₃ to give:
सही उत्तर: घ) acetophenone
This is Friedel–Crafts acylation: C₆H₆ + CH₃COCl → C₆H₅COCH₃ + HCl.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Bromoethane reacts with alcoholic KCN to give a product which, on complete hydrolysis, yields:
सही उत्तर: क) propanoic acid
C₂H₅Br + KCN → C₂H₅CN (propanenitrile); hydrolysis gives C₂H₅COOH, so the chain grows by one carbon.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Ethanal (CH₃CHO) treated with CH₃MgBr, followed by hydrolysis, gives:
सही उत्तर: क) propan-2-ol
A Grignard reagent adds to an aldehyde other than methanal to give a secondary alcohol: CH₃CH(OH)CH₃.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Ozonolysis of 2-methylpropene, (CH₃)₂C=CH₂, followed by reductive work-up (Zn/H₂O), gives:
सही उत्तर: ख) propanone and methanal
The C=C bond is cleaved: (CH₃)₂C= becomes (CH₃)₂C=O (acetone) and =CH₂ becomes HCHO (formaldehyde).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the balanced ionic equation for the oxidation of Fe²⁺ by acidified MnO₄⁻, the mole ratio MnO₄⁻ : Fe²⁺ is:
सही उत्तर: ख) 1 : 5
MnO₄⁻ gains 5 electrons (Mn +7 → +2) while each Fe²⁺ loses 1: MnO₄⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The degree of unsaturation (double-bond equivalent) of benzene, C₆H₆, is:
सही उत्तर: घ) 4
DBE = (2C + 2 − H)/2 = (12 + 2 − 6)/2 = 4 (three C=C bonds and one ring).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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