मेडिकल प्रवेश (CEE) – Physics, Chemistry, Zoology, Botany, MAT
मेडिकल प्रवेश (CEE) – Physics, Chemistry, Zoology, Botany, MAT
Medical Entrance (CEE) – Physics, Chemistry, Biology & MAT · २,०३९ प्रश्न
२,०३९ प्रश्न उपलब्ध। मोड छान्नुहोस्:
CEE 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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Adding a catalyst to a reaction at equilibrium:
सही उत्तर: घ) Does not change the equilibrium constant
A catalyst speeds up forward and backward reactions equally, so equilibrium is reached faster but its position and K are unchanged. Only temperature changes the value of K.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), increasing the pressure will:
सही उत्तर: ग) Shift the equilibrium towards NH₃
By Le Chatelier's principle, increased pressure favours the side with fewer gas moles (2 vs 4), i.e. NH₃. Pressure changes alter position, not the equilibrium constant.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), the value of Δn in Kp = Kc(RT)^Δn is:
सही उत्तर: क) −2
Δn = moles of gaseous products − moles of gaseous reactants = 2 − 4 = −2. Δn = 0 applies to reactions like H₂ + I₂ ⇌ 2HI, where Kp = Kc.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Given: C + O₂ → CO₂, ΔH = −393.5 kJ; CO + ½O₂ → CO₂, ΔH = −283.0 kJ. The enthalpy of formation of CO is:
सही उत्तर: ग) −110.5 kJ mol⁻¹
By Hess's law, subtract the second equation from the first: ΔH = −393.5 − (−283.0) = −110.5 kJ mol⁻¹. Adding the two values instead gives the wrong −676.5 kJ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A reaction is spontaneous at all temperatures when:
सही उत्तर: ख) ΔH is negative and ΔS is positive
With ΔG = ΔH − TΔS, a negative ΔH and positive ΔS make ΔG negative at every temperature. If both are positive, the reaction is spontaneous only at high temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Lithium shows a diagonal relationship with:
सही उत्तर: ख) Magnesium
Li and Mg have similar sizes and charge densities, so they show similar properties (e.g. both form nitrides and carbonates that decompose on heating). Beryllium shows a diagonal relationship with aluminium.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The element with the highest electron affinity (most negative electron gain enthalpy) is:
सही उत्तर: घ) Chlorine
Chlorine has the highest electron affinity. Fluorine is so small that electron–electron repulsion in its compact 2p subshell lowers its value, although F remains the most electronegative element.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The first ionisation energy of nitrogen is higher than that of oxygen because:
सही उत्तर: क) Nitrogen has a stable half-filled 2p subshell
N (2p³) has extra stability from a half-filled p subshell, while removing one electron from O (2p⁴) relieves electron-pair repulsion. A similar anomaly exists between Be and B.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Among the alkali metals Li, Na, K and Cs, the lowest first ionisation energy is shown by:
सही उत्तर: घ) Cs
Ionisation energy decreases down a group as atomic size increases and the outer electron is farther from the nucleus. Li, at the top, has the highest value.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Among the isoelectronic species N³⁻, O²⁻, F⁻ and Na⁺, the one with the largest radius is:
सही उत्तर: घ) N³⁻
In an isoelectronic series, the species with the fewest protons holds the electrons least tightly, so N³⁻ (7 protons) is largest. Na⁺ (11 protons) is the smallest.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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