रसायन विज्ञान – Chemistry MCQ
रसायन विज्ञान – कृषि/वन प्रवेश
Chemistry · Agriculture, Veterinary & Forestry Entrance · ४०९ प्रश्न
४०९ 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 only metal that is liquid at room temperature is:
सही उत्तर: ग) mercury
Mercury melts at about −39 °C; gallium melts at about 30 °C, just above room temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Bleaching powder is added to drinking water supplies mainly to:
सही उत्तर: ग) kill disease-causing germs (disinfection)
It releases chlorine, which kills bacteria and other pathogens.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Biochemical oxygen demand (BOD) of a water sample is a measure of:
सही उत्तर: ग) the amount of biodegradable organic pollution in it
BOD is the oxygen consumed by micro-organisms in decomposing organic matter; a high BOD indicates heavy organic pollution.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Rain is generally called 'acid rain' when its pH falls below about:
सही उत्तर: ग) 5.6
Normal rain is slightly acidic (pH about 5.6) due to dissolved CO₂; SO₂ and NOₓ lower it further.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Flooded rice (paddy) fields are a significant source of which greenhouse gas?
सही उत्तर: ख) Methane
Anaerobic decomposition of organic matter in waterlogged soil produces methane.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Groundwater from tube wells in parts of Nepal's Terai has been found contaminated with naturally occurring:
सही उत्तर: क) arsenic
Arsenic dissolved from sediments has contaminated many Terai tube wells, causing arsenicosis.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Drinking water containing excess fluoride over a long period causes:
सही उत्तर: घ) fluorosis (mottling of teeth and bone damage)
Small amounts of fluoride protect teeth, but excess causes dental and skeletal fluorosis.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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High levels of nitrate in drinking water can cause 'blue baby syndrome', which is:
सही उत्तर: ख) methaemoglobinaemia, reducing the blood's oxygen-carrying capacity
Nitrite formed from nitrate converts haemoglobin into methaemoglobin, which cannot carry oxygen.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Excess nitrate and phosphate from farm run-off cause rapid algal growth in ponds and lakes. This is called:
सही उत्तर: घ) eutrophication
Nutrient enrichment leads to algal blooms; their decay uses up dissolved oxygen and can kill fish.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When urea is applied on the surface of an alkaline soil, some nitrogen is lost to the air mainly as:
सही उत्तर: घ) ammonia gas
Urea hydrolyses to ammonium carbonate; at high pH, NH₄⁺ converts to NH₃ gas, which volatilises.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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