Question

Which one of the following statements is correct?
(a) Manganese salts give a violet borax test in the reducing flame.
(b) From a mixed precipitate of AgCl and AgI, ammonia solution dissolves only AgCl.
(c) Ferric ions give a deep green precipitate on adding potassium ferrocyanide solution.
(d) On boiling a solution having K⁺ , Ca²⁺ and HCO^3– ions we get a precipitate of K₂Ca(CO₃ )₂.

Answer 1

(b) : The solubility product of AgCl, AgBr and AgI at the room temperature are 2.8 × 10^–10, 5.0 × 10^–13 and 8.5 × 10^–17 respectively. Thus, AgI is the least soluble silver halide. 

The lattice energies of AgBr and AgI are even higher because of greater number of electrons in their anions. Consequently, they are even less soluble than AgCl. Due to greater solubility of AgCl than AgI, ammonia solution dissolves only AgCl and forms a complex. 

AgCl + 2NH₄OH ® [Ag(NH₃)₂]Cl + 2H₂O Diammine silver chloride