s-Block ElementsHard
Question
A metal (M) burns with dazzling brilliance in air to give a white powder. The white powder reacts with water to form a white precipitate and a colourless gas with a characteristic smell. The metal (M) decomposes hot water but not cold water, liberating the inflammable hydrogen gas. The metal(M) is :
Options
A.K
B.Ca
C.Mg
D.Rb
Solution
Hydrogen is liberated when Mg reacts with hot water. Rb, K and Ca gives hydrogen gas even with cold water.
Mg + O2 → MgO ; Mg + N2 → Mg3N2
Mg3N2 + 6H2O → 3Mg(OH)2 + 2NH3 ↑
Mg + 2H2O (hot) → Mg(OH)2 + H2.
Mg + O2 → MgO ; Mg + N2 → Mg3N2
Mg3N2 + 6H2O → 3Mg(OH)2 + 2NH3 ↑
Mg + 2H2O (hot) → Mg(OH)2 + H2.
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