`A overset("Calcination")rarr CaO + MgO + underset("Colourless gas")((B))`
When the colourless gas `(B)` is passed through lime water, initially a milky solution is obtained and on excess passage of gas `(B)` through the lime water, milkiness disappears.
Lime water is.

Options

A. `CaO`
B. `CA(OH)_(2)`
C. `CaCO_(3)`
D. `CaCO_(3) .Ca(OH)_(2)`

Answer

B

Explanation

Since on calcination, i.e., heating the ore `(A)` is limited supply of `O_(2)`, both `CaO` and `MgO` are formed along with a colourless gas `(B). (A)` is `CaCO_(3).MgCO_(3).(A)` is known as dolomite.
`CaCO_(3).MgCO_(3) overset("Calcination")rarr CaO + MgO + underset((B))(2CO_(2))`
`CO_(2) + underset("Lime water")(Ca(OH)_(2))rarr underset("Milkiness") (CaCO_(3))+ H_(2) O`
`CaCO_(3) +H_(2) O + CO_(2) rarr underset("Milkiness disappears") (Ca(HCO_(3))_(2))`
On passing `CO_(2)` through lime water `[Ca(OH)_(2)]` solution, initially lime water turns milky due to formation of `CaCo_(3)`, which is insoluble in water. On excess passage of `CO_(2)` gas through lime water, milkiness disppears due to formation of `Ca(HCO_(3))_(2)`. Hence.
(iv) Limewater is `Ca(OH)_(2)` solution.