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Chemistry

Distinguish between the following pairs of compounds using the reagent given in the bracket.

(i) Manganese dioxide and copper [II] oxide [using conc. HCl]

(ii) Ferrous sulphate solution and ferric sulphate solution [using sodium hydroxide solution]

Practical Chemistry

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Answer

(i) When each of the compound is heated with conc. hydrochloric acid, greenish yellow (chlorine) gas is evolved in case of manganese dioxide and filtrate is brownish in colour whereas, no chlorine gas is evolved in case of copper (II) oxide and filtrate is bluish in colour.

MnO2 + 4HCl ⟶ MnCl2 + 2H2O + Cl2

CuO + 2HCl ⟶ CuCl2 + H2O

(ii) When sodium hydroxide is added to the two solns., ferrous sulphate solution gives a dirty green ppt. of Fe(OH)2 whereas, ferric sulphate solution forms a reddish brown ppt. of Fe(OH)3. Hence, the two compounds can be distinguished.

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