An unknown solid is entirely soluble in water. On addition of dilute HC1, a prec

Question

An unknown solid is entirely soluble in water. On addition of dilute HC1, a precipitate forms. After the precipitate is filtered off, the pH is adjusted to about 1 and H_2 S is bubbled in; a precipitate again forms. After filtering off this precipitate, the pH is adjusted to 8 and H_2S is again added; no precipitate forms. No precipitate forms upon addition of (NH_4)_2HPO_4. The remaining solution shows a yellow color in a flame test. Based on these observations, which of the following compounds might be present, which are definitely present, and which are definitely absent. Drag the appropriate items to their respective bins.

Explanation / Answer

Part A : Ions qualitative analysis

Might be present

Na2SO4

Are definitely present

HgO, Pb(NO3)2 [both give insoluble chlorides upon addition of dil. HCl]

CdS, Cd(NO3)2 [forms insoluble sulfide upon addiiton of H2S under acidic medium]

Are definitely absent

ZnSO4

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