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Chlorine evolved by the reaction of 45.3...

Chlorine evolved by the reaction of 45.31g of pyrolusite (impure) and excess of HCl is found to combine completely with the hydrogen produced by the reaction of 10g of magnesium and excess of dilute hydrochloric acid. Find the percentrage of purity of `MnO_(2)` in the given pyrolusite.

Text Solution

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`underset(24g)(Mg)+underset((2xx36.5g))(2HCl) to MgCl_(2)+underset(2g)(H_(2))`
`underset(87g)(MnO_(2))+4HCl to MnCl_(2)underset(71g)(+Cl_(2))+2H_(2)O`
`underset(2g)(H_(2))+underset(71g)(Cl_(2)) to 2HCl`
2g of hydrogen obtained by using 24g of Mg will combine by using 24g of Mg will combine completely with 71g of chlorine produced from 87g of ppure `MnO_(2)`.
Thus, when 10g of Mg are used, the mass of the pure `MnO_(2)` required is =`(87)/(4)xx10-36.25g`
So, 45.31g of pyrolusite contain `MnO_(2)` (pure)=36.25
100g of pyrolusite contain `MnO_(2)` (pure) `=(36.25)/(45.31)xx100=80.00g`
Percentage of purity=80.00g
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