Steps for verifying SO42-: add BaCl2 and then add HCl.

Steps for verifying SO42-: add BaCl2 and then add HCl.

Incorrect. If there is Ag+ in the solution, adding BaCl2 first will also produce white precipitation, and then adding HCl precipitation will not be dissolved, which will mislead the sulfate test. The correct sequence is to add HCl first. If there is no precipitation (i.e. there is no silver ion in the solution) and then adding barium chloride, white precipitation will be produced, and then adding hydrochloric acid precipitation will not disappear, which means SO42- is present.

Incorrect. If there is Ag+ in the solution, adding BaCl2 first will also produce white precipitation, and then adding HCl precipitation will not be dissolved, which will mislead the sulfate test. The correct sequence is to add HCl first. If there is no precipitation (i.e. there is no silver ion in the solution) and then adding barium chloride, white precipitation will be produced, and then adding hydrochloric acid precipitation will not disappear, which indicates SO42-

Remove Ca, Mg, SO4 ions from crude salt. Add excess NaOH, excess Na2CO3, excess BaCl2, and appropriate amount Add excess NaOH, excess Na2CO3, excess BaCl2, appropriate hydrochloric acid, right? NaOH first or Bacl2 first?

Add excess NaOH, excess Na2CO3, excess BaCl2, and appropriate hydrochloric acid.
Na2CO3 must be placed behind the NaOH,BaCl2.
It doesn't matter if you add NaOH first or Bacl 2 first.