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# Which of the following statements is NOT Correct?

(1) Silver flouride is fairly soluble in water

(2) Silver Nitrate is a thermally stable substance

(3) Silver Nitrate gives white precipitate with sodium thiosulphate which changes its colour to yellow, brown and finally black due to the formation of silver

(4) Silver nitrate gives white precipitate with concentrated solution of sodium thiosulphate

$\begin{array}{1 1} \text{(A) All statements are incorrect} \\ (B) \text{Only (2), (3) and (4) are incorrect} \\ \text{(C) Only (2) and (3) are incorrect } \\ \text{ (D) Only (1) and (3) are incorrect }\end{array}$

(1) Silver flouride is fairly soluble in water $\rightarrow$ Silver halides, except for silver fluoride, are very insoluble in water. The solubility of silver halides decreases down the periodic table: $\; AgF \; > AgCl > AgBr > AgI$
(2) Silver Nitrate is a thermally stable substance $\rightarrow$ Silver nitrate(aq) also decomposes(g) when heated: $2 AgNO_3 \rightarrow 2 Ag + O_2 + 2 NO_2$
(3) Silver Nitrate gives white precipitate with sodium thiosulphate which changes its colour to yellow, brown and finally black due to the formation of silver $\rightarrow$ Addition of silver nitrate gives a white precipitate of silver thiosulphate, $Ag_2S_2O_3$, which is immediately dissolved if the sodium thiosulphate is in excess. The precipitate is rather unstable, and decomposes on standing, and more rapidly on heating, -giving black silver sulphide and sulphuric acid, $Ag_2S_2O_8 + H_2O = Ag_2S + H_2SO_4$
(4) Silver nitrate gives white precipitate with concentrated solution of sodium thiosulphate $\rightarrow$ With a concentrated solution. no precipitate is formed. Instead, we get a complex ion $[Ag(S_2O_3)_2]^{3-}.$