Determine the weight of CaO required to remove the hardness of a sample of `10^(5)` L water, 1 L of which contains 1.62g of Ca`("HCO"_(3))_(2)`.

Explanation

When CaO is added to a sample of hard water containing Ca`("HCO"_(3))_(2)`, dissolved bicarbonate is precipitated as `"CaCO"_(3)` and as a result, the hardness is removed.
CaO`" " + " "underset(" molecular mass = 56 molecular mass = 162 ")(Ca("HCO"_(3))_(2))` = 2`"CaCO"_(3)uarr + H_(2)O`
1 L of water contains 1.62 g of `Ca("HCO"_(3))_(2)`.
`therefore " "10^(5)`L of water contains `1.62 xx 10^(5)` g of `Ca("HCO"_(3))_(2)`.
According to the above equation,
For removing 162 g Ca`("HCO"_(3))_(2),` 56 g CaO is required.
`therefore` Amount of Cao required = `(56 xx 1.62 xx 10^(5))/(162)g = 56 xx 10^(3)` g