What is the first step in the six steps of preparation for soluble salts via the characteristic method?

• A. Add excess insoluble solid to the beaker until it stops reacting
• B. Filter the excess solid
• C. Evaporate immediately
• D. Allow crystals to form then filter

Answer: (A)

The first step is to add excess insoluble solid to the acid until it stops reacting. Using excess solid guarantees the acid is driven to completion, so the soluble salt is produced in the solution and no unreacted acid remains. Once the reaction ceases, you can filter off the excess solid, leaving a clear solution that contains the desired salt. The later steps then focus on concentrating and crystallising that salt. Filtering first or evaporating immediately would not ensure complete reaction or give a clean solution to crystallise from.