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
-
Which element has the most negative (highest) electron gain enthalpy?
सही उत्तर: ग) Chlorine
Chlorine has the highest electron affinity. Fluorine's value is lower because its small 2p subshell causes strong repulsion with the incoming electron.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
Among B, C, N and O, the element with the highest first ionisation energy is:
सही उत्तर: ख) N
Nitrogen's half-filled 2p³ subshell is extra stable, so its first ionisation energy exceeds that of oxygen. Oxygen is lower because removing one paired 2p electron relieves electron repulsion.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
Among Na, Mg, Al and Si, the element with the largest atomic radius is:
सही उत्तर: क) Na
Atomic radius decreases across a period as nuclear charge increases with the same shell, so sodium, at the start of period 3, is largest. Silicon is the smallest of the four.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
The number of neutrons in an atom of ²³⁵U (atomic number 92) is:
सही उत्तर: घ) 143
Neutrons = mass number − atomic number = 235 − 92 = 143. 92 is the number of protons.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
Which pair of atoms are isotones (same number of neutrons)?
सही उत्तर: ग) ¹⁴C and ¹⁶O
¹⁴C has 14 − 6 = 8 neutrons and ¹⁶O has 16 − 8 = 8 neutrons, so they are isotones. ³⁵Cl and ³⁷Cl are isotopes (same Z, different neutrons).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
Which pair of atoms are isobars?
सही उत्तर: ख) ⁴⁰Ar and ⁴⁰Ca
Isobars have the same mass number but different atomic numbers, as ⁴⁰Ar (Z = 18) and ⁴⁰Ca (Z = 20) do. ¹²C and ¹⁴C have the same atomic number, so they are isotopes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
The number of unpaired electrons in a nitrogen atom in its ground state is:
सही उत्तर: क) 3
Nitrogen is 1s² 2s² 2p³, and by Hund's rule the three 2p electrons occupy separate orbitals, giving 3 unpaired electrons. Five is the total number of valence electrons, not unpaired ones.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
According to Heisenberg's uncertainty principle, the product Δx·Δp is:
सही उत्तर: घ) ≥ h/4π
Heisenberg's principle states Δx·Δp ≥ h/4π, so position and momentum cannot both be known exactly. The product can never be smaller than h/4π.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
Which spectral series of the hydrogen atom lies in the visible region?
सही उत्तर: ग) Balmer series
Balmer lines arise from transitions ending at n = 2 and fall in the visible region. The Lyman series (ending at n = 1) lies in the ultraviolet.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
The ground-state energy of the electron in a He⁺ ion is:
सही उत्तर: ख) −54.4 eV
For hydrogen-like species Eₙ = −13.6 Z²/n² eV; with Z = 2 and n = 1, E = −13.6 × 4 = −54.4 eV. −27.2 eV results from multiplying by Z instead of Z².
💬 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।
नमस्ते! पाठ्यक्रम, सामान्य ज्ञान, भाषा परीक्षा वा कुनै प्रश्नको उत्तर बुझ्न सोध्नुहोस्।
AI ले गल्ती गर्न सक्छ। महत्वपूर्ण कुरा आधिकारिक स्रोतमा जाँच्नुहोस्।