A silver halide purification process involves three consecutive reactions conducted…
CHEMISTRY · Multi-part · A Level · Chemistry · Transition metals and their chemistry · Transition metals and their chemistry
Problem
A silver halide purification process involves three consecutive reactions conducted in the same reaction vessel at 25 °C.
Step 1 An aqueous solution containing 0.15 M AgNO₃ is mixed with an equal volume of 0.20 M NaCl. A solid forms immediately.
Step 2 After the solid is separated, a concentrated NH₃(aq) solution is added until the mixture becomes clear once again.
Step 3 Concentrated HNO₃ is then added drop-wise to the clear solution, and a solid re-appears.
Assume the volume changes caused by the additions do not affect the qualitative outcome. Water is the solvent in every step.
(a) Write the complete ionic equation for each of the three steps described.
(b) For each step, identify all spectator ions and circle any chemical species that serve as intermediates (produced in one step and consumed in a later step).
(c) Derive the overall net ionic equation for the entire three-step sequence by appropriately canceling species that appear on both sides when the individual steps are added together.
(d) Explain, with specific reference to atom and charge counts, how the overall net ionic equation you obtained in part (c) illustrates the laws of conservation of mass and charge even though observable solids appear and disappear during the procedure.