Question

Explain why the addition of NH₃ or HNO₃ to a saturated solution of Ag₂CO₃ in contact with solid Ag₂CO₃ increases the solubility of the solid.

a) NH₃ and HNO₃ react with Ag₂CO₃ to form a more soluble complex.
b) NH₃ and HNO₃ decrease the temperature, promoting dissolution.
c) NH₃ and HNO₃ react with Ag₂CO₃ to form an insoluble precipitate.
d) NH₃ and HNO₃ increase the pressure, promoting dissolution.

Answer 1

The solubility of Ag2CO3 increases with the addition of NH3 because NH3 forms a complex with Ag+, reducing Ag+ concentration and increasing solubility. For HNO3, its addition provides excess H+ ions that react with CO3^2- ions, reducing their concentration and increasing the solubility of Ag2CO3. The correct option is A.

Step-by-step explanation:

The addition of NH₃ or HNO₃ to a saturated solution of Ag₂CO₃ in contact with solid Ag₂CO₃ increases the solubility of the solid for different reasons. When NH₃ is added to the solution, it acts as the conjugate base of a weak acid and forms a complex ion with Ag+.

This reaction reduces the concentration of silver ions in the solution by formation of [Ag(NH₃)₂]+, which in turn increases the solubility of Ag₂CO₃ due to Le Chatelier's principle. Conversely, HNO₃ is the conjugate acid of a strong base (NO₃), so its addition doesn't change the solubility directly by forming complexes.

Instead, the presence of excess H+ from HNO₃ shifts the equilibrium by reacting with the CO₃2- ions, decreasing their concentration, and thus increasing the solubility of Ag₂CO₃