Question:
One mole of an unknown compound was treated with excess water and resulted in the evolution of two moles of a readily combustible gas. The resulting solution was treated with CO$_2$ and resulted in the formation of white turbidity. The unknown compound is
One mole of an unknown compound was treated with excess water and resulted in the evolution of two moles of a readily combustible gas. The resulting solution was treated with CO$_2$ and resulted in the formation of white turbidity. The unknown compound is
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Hydrides + water → hydrogen gas + hydroxide.
Updated On: May 1, 2026
- Ca
- CaH$_2$
- Ca(OH)$_2$
- Ca(NO$_3$)$_2$
- CaSO$_4$
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The Correct Option is B
Solution and Explanation
Concept:
Metal hydrides react with water to produce hydrogen gas.
Step 1: Reaction with water.
\[ \text{CaH}_2 + 2H_2O \rightarrow Ca(OH)_2 + 2H_2 \] 2 moles of H$_2$ produced → matches given.
Step 2: CO$_2$ test.
\[ Ca(OH)_2 + CO_2 \rightarrow CaCO_3 \downarrow \] White turbidity confirms Ca(OH)$_2$ formation.
Step 3: Conclusion.
Original compound is CaH$_2$.
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