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Describe methods to remove the temporary Hardness of water (i) Boiling (ii) Clark.s is method. |
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Answer» Solution :(i)Boiling : During boiling, the soluble `Mg(HCO_3)_2` is converted into insoluble `Mg(OH)_2` and `Ca(HCO_3)_2` is changed to insoluble `CaCO_3`. It is because of HIGH solubility product of `Mg(OH)_2` as compared to that of `MgCO_3`, that `Mg(OH)_2` is PRECIPITATED. These precipitates can be removed by filtration. Filtrate thus obtained will be soft water. `Mg(HCO_3)_2 overset"HEATING"to Mg(OH)_2 darr + 2CO_2 uarr` `Ca (HCO_3)_2 overset"heating" to CaCO_3 darr + H_2O + CO_2 uarr` (ii) Clark.s method : In this method calculated amount of lime is added to hard water. It precipitates out CALCIUM carbonate and magnesium hydroxide which can be filtered off. `Ca(HCO_3)_2 + Ca(OH)_2 to 2CaCO_3 darr + 2H_2O` `Mg(HCO_3)_2 + 2CA(OH)_2 darr to 2CaCO_3darr + Mg(OH)_2 darr + 2H_2O` |
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