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Permanent hardness due to `Mg^(2+)` ions is best removed byA. `Ca(OH)_(2)`B. `Na_(2)CO_(3)`C. `Na_(2)CO_(3)+Ca(OH)_(2)`D. None of these |
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Answer» Correct Answer - C `Ca(OH)_(2)` removes the permanent hardness due to `Mg^(2+)` ion, but it produces `Ca^(2+)` ions which are removed by `Na_(2)CO_(3)`. `Ca^(2+)+Ca(OH)_(2)rarr Mg(OH)_(2)darr+Ca^(2+)` `Ca(OH)_(2)+Na_(2)CO_(3) rarr CaCO_(3)darr + 2 Na ^(+)` `Ca(OH)_(2)` or `Na_(2)CO_(3)` alone cannot remove the permanent hardness. |
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