When 1 mole of a substance `(X)` was treated with an excess of water, 2 moles of readily combustible gas were produced along with solution which when reacted with `CO_(2)` gas produced a white turbidity. The substance `(X)` could be

Options

A. Ca
B. `CaH_2`
C. `Ca(OH)_2`
D. `Ca(NO_3)_2`

Answer

B

Explanation

Calcium hydride `(CaH_2)` on reaction with excess water evolves two moles of readily combustible `H_2` gas and one mole of calcium hydroxide . The solution containing `Ca(OH)_2` on treatment with `CO_2` gas forms white turbidity due to the formation of `CaCO_3`.
`CaH_2(s) + 2H_2O to Ca(OH)_2 + underset("Combustible gas ")(2H_2(g))`
`Ca(OH)_2 (aq) + CO_2(g) to underset("Calcium carbonate (white turbidity)")(CaCO_3(s)) + H_2O`