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Washing soda `(Na_(2)CO_(3).10 H_(2)O)` is widely used in softening of hard water. If 1 L of hard water requires 0.0286 g of washing soda, the hardness of `NaOH` in ppm is |
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Answer» Correct Answer - 4 Mw of washing soda `=286`, Mw of `NaOH=40" g mol"^(-1)` `Ca(OH)_(2)+Na_(2)CO_(3) rarr CaCO_(3)+2 NaOH` `0.0286 g Na_(2)CO_(3). 10 H_(2)O =0.0286/(286//2)xx10^(3)=0.2` meq 0.2 meq of `Na_(2)CO_(3)=0.2/2` mmol of `NaOH` in 1L `=(0.1xx10^(-3))xx40g` in `10^(3)` mL. `=0.01 g` in `10^(3)` mL ppm `=(4xx10^(-3)xx10^(6))/10^(3)=4` ppm. |
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