A water is said to be soft water if it produces sufficient foam with the soap and water that does not produce foam with soap is known as hard water. Hardness has been classified into two types (i)Temporary hardness (ii) Permanent hardness.
Temporary hardness is due to presence of calcium and magnesium bicarbonate. It is simply removed by boiling as
`Ca(HCO_(3))_(2)overset(Delta)rarr CaCO_(3)darr+CO_(2)uarr+H_(2)O`
`Mg(HCO_(3))_(2)overset(Delta)rarr MgCO_(3)darr+CO_(2)uarr+H_(2)O`
temporary hardness can also be removed by addition of slaked lime, `Ca(OH)_(2)`
`Ca(HCO_(3))_(2)+Ca(OH)_(2)to2CaCO_(3)darr+2H_(2)O`
permanent hardsness is due to presencce of sulphates and chlorides of Ca,Mg,etc. It is removed by washing soda as
`CaCl_(2)+Na_(2)CO_(3)toCaCO_(3)darr+2NaCl`
`CaSO(4)+Na_(2)CO_(3)to CaCO_(3)darr+Na_(2)SO_(4)`
Permanent hardness also removed by ion exchange resin process as
`2RH+Ca^(2+) to R_(2)Ca+2H^(+)`
`2ROH+SO_(4)^(2-)toR_(2)SO_(4)+2OH^(-)`
The degree of hardness of water is measured in terms of PPm of `CaCO_(3)` 100 PPm means 100 g of `CaCO_(3)` is present in `10^(6)` g of `H_(2)O`. If any other water sample which contain 120 PPm of `MgSO_(4)`, hardness in terms of `CaCO_(3)` is equal to =100 PPm.
What is the mass of `Ca(OH)_(2)` required for 10 litre of water remove temporary hardness of 100 PPm due to `Ca(HCO_(3))_(2)` ?

Options

A. 100 ppm
B. 200 ppm
C. 300 ppm
D. None of these

Answer

C