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An aqueous solution of a crystalline salt reacts with dilute HCl to give a yello...



Dicussion (1)

  • The Correct Answer is A.

    Firstly, the two gases that turn dichromate paper green are H2S and SO2. Also, we know that what we want is a crystalline salt and we know that every crystalline salt usually have at least a mole Water of Crystalization attached to the Salt, that leaves us with just A and B.

    Out of the two only \( Na_{2}S_{2}O_{3}.5H_{2}O \) contains Sulphur and thus is able to give out SO2 and deposit of Sulphur (Yellow Deposit) on reacting with HCl. \( Na_{2}S \) on the other hand will give out H2S but no yellow deposit of Sulphur and this is not what we want.

    We can therefore reach a logical conclusion that the CORRECT ANSWER is A, \( Na_{2}S_{2}O_{3}.5H_{2}O \).