विज्ञान – Science MCQ
विज्ञान – डिप्लोमा प्रवेश
Science · CTEVT Diploma Engineering Entrance · ४०५ प्रश्न
४०५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
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 volume occupied by 2 moles of a gas at STP is:
सही उत्तर: क) 44.8 L
One mole of any gas at STP occupies 22.4 L, so 2 moles occupy 44.8 L. 22.4 L is for only one mole.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When 100 g of calcium carbonate is completely decomposed by heating (CaCO₃ → CaO + CO₂), the mass of carbon dioxide formed is (Ca = 40, C = 12, O = 16):
सही उत्तर: क) 44 g
100 g CaCO₃ is 1 mole and gives 1 mole of CO₂ = 44 g. 56 g is the mass of CaO formed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the balanced equation N₂ + x H₂ → 2NH₃, the value of x is:
सही उत्तर: घ) 3
There are 6 H atoms in 2NH₃, so 3H₂ is needed. 6 would put 12 hydrogen atoms on the left.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Calcium has valency 2 and the phosphate radical has valency 3. The formula of calcium phosphate is:
सही उत्तर: ख) Ca₃(PO₄)₂
Criss-crossing valencies gives Ca₃(PO₄)₂, where total positive charge 3 × 2 = 6 equals total negative charge 2 × 3 = 6. Ca₂(PO₄)₃ wrongly places the valencies.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Aluminium has valency 3 and oxygen has valency 2. The formula of aluminium oxide is:
सही उत्तर: घ) Al₂O₃
By criss-crossing the valencies, Al gets 2 and O gets 3, giving Al₂O₃. Al₃O₂ results from not crossing the valencies.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The percentage of nitrogen by mass in ammonia (NH₃) is about (N = 14, H = 1):
सही उत्तर: घ) 82.4%
% N = 14/17 × 100 ≈ 82.4%. 17.6% is the percentage of hydrogen.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of molecules present in 0.5 mole of a gas is:
सही उत्तर: ग) 3.011 × 10²³
Number of molecules = moles × Avogadro's number = 0.5 × 6.022 × 10²³ = 3.011 × 10²³. 6.022 × 10²³ is for one full mole.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of moles in 36 g of water is (H = 1, O = 16):
सही उत्तर: क) 2
Molar mass of H₂O = 18 g/mol, so moles = 36/18 = 2. 648 comes from multiplying instead of dividing.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 50 kg person stands on a planet where the acceleration due to gravity is twice that on Earth (take Earth's g = 10 m/s²). The person's weight there is:
सही उत्तर: ग) 1000 N
Weight = m × g = 50 × 20 = 1000 N. The mass remains 50 kg; 500 N is the weight on Earth.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Light from the Sun travels about 1.5 × 10⁸ km to reach the Earth at 3 × 10⁵ km/s. The time taken is about:
सही उत्तर: ग) 8.3 minutes
t = d/v = 1.5 × 10⁸ / 3 × 10⁵ = 500 s ≈ 8.3 minutes. This is why we see the Sun as it was about 8 minutes ago.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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