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Question
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be:
Options
calcium
carbon
silicon
iron
Solution
calcium
Explanation:
Calcium (Ca) combines with oxygen to form Calcium oxide (CaO) with a very high melting point. It dissolves in water to form Calcium hydroxide.
\[\ce{2Ca + O2 -> 2CaO}\]
\[\ce{CaO + H2O -> \underset{(soluble)}{\underset{Calcium hydroxide}{Ca(OH)2}}}\]
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