For the following scenarios, determine what ions are definitely present and which are definitely absent. You may have one or more ions that you cannot say is definitely present or absent - if you don't do a test for the ion, you cannot tell one way or other so it would not be included on either list.
1. You have an unknown that may contain one or more of the following anions: SO42-, CO32-, PO43-, Cl-, Br-, I-. When BaCl2 is added to this unknown, a white precipitate forms. When acid is added no bubbles formed and part of the precipitate dissolves. When ammonium molybdate is added a yellow precipitate is formed. Upon addition of methylene chloride and potassium nitrate to the unknown, two layers form with the bottom layer turning a pink/purple. When methylene chloride and potassium permanganate are added to the unknown, two layers form with a colorless bottom layer. When the unknown is treated with silver nitrate, a precipitate forms that dissolve in ammonia.
a. What ions are definitely present?
b. What ions are definitely absent?
2. You have an unknown that may contain one or more of the following anions: SO42-, CO32-, PO43-, Cl-, Br-, I-. When BaCl2 is added to this unknown, a white precipitate form which does not dissolve at all in nitric acid. Upon the addition of sulfuric acid, no bubbling was seen. The addition of silver nitrate resulted in the formation of off-white solid which partly dissolved in nitric acid. Upon the addition of methylene chloride and potassium nitrate to the unknown, two layers form with a colorless bottom layer.
a. What ions are definitely present?
b. What ions are definitely absent?