1). briefly explain the problem that arises if Fe3+ ion is not completely removed from the solution containing representative Group B-E cations in this Procedure.
2). Describe the method for checking for completeness of precipitation.
3). Briefly explain why precipitates are usually rinsed with distilled water before they are tested further.
4). A student analyzing an unknown solution containing some of the cations studied in this module records the following results. At each step indicate which cations are present and which have been proven absent from the unknown mixture. (1). 4 drops of 6M HCl solution are added to the unknown solution and no precipitate forms. (2). The pH of the solution from (1) is raised to 9.5 by addition of 6M NH3 solution. Acloudy, red-brown reaction mixture results.