【Daily Question】Chemical Analysis Version 2021.12.21
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What is the endpoint color when using the Volhard method to determine the Ag+ content in water? A、Red ； B、Pure blue ； C. Yellow-green ； D, Blue-violet A
A: In an acidic medium, a standard solution of ammonium thiocyanate (NH4SCN) is used to directly titrate the solution containing Ag+. Once the silver thiocyanate (AgSCN) precipitate has formed completely, any excess SCN- reacts with Fe3+ to form red complex ions, indicating that the titration endpoint has been reached.