A pale green crystalline metal salt of (X) dissolves freely in the water. It gives a brown precipitate on the addition of aq. $NaOH$ . The metal salt solution also gives a black precipitate on bubbling $H_{2} S$ in aqueous medium. An aqueous solution of the metal salt decolourises the pink colour of the permanganate solution. The metal in the metal salt solution is:

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answer is A.

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Detailed Solution

Concept- If a salt reacts with aq.

NaOH

to produce a product, it must be acidic in nature since only then will it be able to react with a base. Copper salts are often blue in colour, while lead salts are white or black in colour, iron salts are greenish in colour, and aluminium salts are white.
Thus, Iron is the metal in the metal salt solution (Fe).
Ferrous sulphate is a pale green crystalline metal salt (

FeS O_{4}

). When let to stand, it quickly dissolves in water and produces a brown ppt. of basic ferric sulphate

Fe (OH) (S O_{4}) .

4 FeS O_{4} + 2 H_{2} O + O_{2} \to 4 Fe (OH) (S O_{4})

On bubbling

H_{2} S

, the metal salt solution likewise produces a black ppt.

{{Fe}^{2 +} + H}_{2} S \to FeS + 2 H^{+}

The pink colour of the permanganate solution is decolourised by an aqueous solution of the metal salt, which produced colourless products.

10 FeS O_{4} + 8 H_{2} S O_{4} + 2 KMn O_{4} \to 5 {Fe}_{2} (S O_{4})_{3} + 2 MnS O_{4} + K_{2} S O_{4} + 8 H_{2} O

As a result, the right answer is iron (Fe), option 1, because the metal (X) contained in the solution satisfies all of the prerequisites.
Hence, the correct option is (1).

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