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A sample of hard water contains 20 mg of Ca^(2+) ions per litre. How many milliequivalents of Na_(2)CO_(3) would be required to soften 1 litre of the sample ? |
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Answer» Solution :`underset(40G)(Ca^(2+))+underset(2xx23+12xx3xx16=106g)(Na_(2)CO_(3))rarrCaCO_(3)+2Na^(+)` `"40 g "Ca^(2+)" ions react with "Na_(2)CO_(3)=106g` `THEREFORE"20 mg, i.e., "20xx10^(-3)gCa^(2+)` ions will react with `Na_(2)CO_(3)=(106)/(40)xx20xx10^(-3)g=5.3xx10^(-2)g` `"Equivalent wt. of "Na_(2)CO_(3)=("Mol. wt.")/(2)=(2xx23+12+3xx16)/(2)=53` `therefore""5.3xx10^(-2)g Na_(2)CO_(3)=(5.3xx10^(-2))/(53)"g EQ."=10^(-3)"g eq. = 1 millieq."` |
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