Describe how to analyze a solution of NaI by using the Volhard

titration.

The Volhard method is an indirect or back titration method in which an excess of a standard solution of silver nitrate is added to a chloride containing sample solution. The excess silver is then back titrated using a standardized solution of potassium or ammonium thiocyanate with ferric ion as an indicator.

We use the Volhard method to analyze certain anions that react with Ag⁺ cation, for example iodide in NaI. First we add AgNO₃ to the NaI solution and solid AgI forms:

${\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{l}}^{-}\left(\mathrm{aq}\right)𝆏\mathrm{Agl}\left(\mathrm{s}\right)$

The solution is then filtered and washed with HNO₃ to collect Ag⁺.

Then Fe(NO₃)₃ is added to put free Fe³⁺ in the solution. KSCN is added to solid AgSCN forms:

${\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{SCN}}^{-}\left(\mathrm{aq}\right)𝆏\mathrm{AgSCN}\left(\mathrm{s}\right)$

At the end, when all Ag⁺ reacts, SCN^- reacts with Fe³⁺ and forms a red complex and that complex shows us the end point of the titration.

Hence, the final answer is that complex shows us the end point of the titration.