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 normality of a 0.5 M H₂SO₄ solution is:
सही उत्तर: ख) 1 N
H₂SO₄ is dibasic (n-factor 2), so N = M × 2 = 1 N. 0.25 N comes from dividing by the n-factor instead of multiplying.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The molarity of a solution containing 4 g of NaOH dissolved in 500 mL of solution is:
सही उत्तर: क) 0.2 M
Moles of NaOH = 4/40 = 0.1 mol, and molarity = 0.1/0.5 L = 0.2 M. 0.1 M comes from forgetting to divide by the volume in litres.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A gas occupies 300 mL at 27 °C. At constant pressure, its volume at 127 °C will be:
सही उत्तर: ग) 400 mL
By Charles's law, V₂ = V₁ × T₂/T₁ = 300 × 400/300 = 400 mL. Temperatures must be in kelvin; using °C directly gives the wrong answer.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The value of the universal gas constant R in SI units is:
सही उत्तर: क) 8.314 J mol⁻¹ K⁻¹
R = 8.314 J mol⁻¹ K⁻¹. The value 0.0821 is in L atm mol⁻¹ K⁻¹ and 1.987 is in cal mol⁻¹ K⁻¹, so those numbers do not match these units.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The unusually high boiling point of water compared with H₂S is mainly due to:
सही उत्तर: घ) Hydrogen bonding
Water molecules are linked by strong intermolecular hydrogen bonds, which need extra energy to break. H₂O actually has a lower molar mass (18) than H₂S (34), so mass cannot explain it.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which element has the highest (most negative) electron gain enthalpy?
सही उत्तर: ख) Chlorine
Chlorine releases the most energy on gaining an electron. Fluorine is smaller, so electron-electron repulsion in its compact 2p subshell makes its value less negative than chlorine's.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The modern periodic law states that the properties of elements are a periodic function of their:
सही उत्तर: घ) Atomic numbers
Moseley showed that atomic number is the more fundamental property, which led to the modern periodic law. Mendeleev's original law was based on atomic masses.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following elements has the lowest first ionization energy?
सही उत्तर: ग) Na
Na has a single 3s electron that is easily removed, so it has the lowest first ionization energy in period 3. Al is lower than Mg, but still higher than Na.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of neutrons in a ²³₁₁Na atom is:
सही उत्तर: घ) 12
Neutrons = mass number − atomic number = 23 − 11 = 12. 11 is the number of protons (and electrons in the neutral atom).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Isotopes of an element have:
सही उत्तर: ख) The same atomic number but different mass numbers
Isotopes such as ¹²C and ¹⁴C have the same number of protons but different numbers of neutrons. Atoms with the same mass number but different atomic numbers are isobars.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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