SCIENCE
CHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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turns into calcium oxide and carbon dioxide
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turns into calcium hydroxide
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Either A or B
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None of the above
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Detailed explanation-1: -CaO(s) + CO2(g) → CaCO3(s) However, above about 1200 K the opposite reaction occurs, calcium carbonate decomposes to form calcium oxide and gives off carbon dioxide. This is what happens in lime kilns where limestone (calcium carbonate) is heated to form lime (calcium oxide).
Detailed explanation-2: -Carbon dioxide reacts with limewater (a solution of calcium hydroxide, Ca(OH) 2), to form a white precipitate (appears milky) of calcium carbonate, CaCO 3. Adding more carbon dioxide results in the precipitate dissolving to form a colourless solution of calcium hydrogencarbonate.
Detailed explanation-3: -When heated above 840°C, calcium carbonate decomposes, releasing carbon dioxide gas and leaving behind calcium oxide – a white solid. Calcium oxide is known as lime and is one of the top 10 chemicals produced annually by thermal decomposition of limestone.
Detailed explanation-4: -In an endothermic reaction, heat energy is added, whereas in an exothermic reaction, heat energy is given out. Calcium carbonate undergoes thermal decomposition to form calcium oxide and carbon dioxide.
Detailed explanation-5: -Calcium oxide + carbon dioxide → Calcium carbonate.