Question

Given an unknown sample that could contain Cr³⁺, Mn²⁺, and/or Fe²⁺ you strip the metal ions from pieces of chalk using hydrochloric acid, subsequently concentrating the solutions and adding sodium hydroxide. You then add sodium hypochlorite and ammonium hydroxide. After boiling and centrifuging the product, you isolate the solution by decantation. You wash the remaining solid twice with water and sodium hydroxide. Then, water and sulfuric acid are added to this solid. The decanted solution is yellow and you decide the skip to the next step. To you solution made by adding water and sulfuric acid to the initial solid, you stir the solution, add hydrogen peroxide, and boil. After adding water to the boiled solution, you separate it into two test tubes. To one tube, you add potassium thiocyanate, and the solution turns a deep red color. To the second tube, you add a few grains of sodium bismuthate. You mix this solution and centrifuge it. You only observe a clear solution.

Part A.

Which cations are present in your unknown sample?

List the metal symbols in alphabetical order, separated by commas.

Part B.

Which cations are not present in your unknown sample?

List the metal symbols in alphabetical order, separated by commas.

Part C.

Which of these group III cations may or may not be in your unknown sample?

List the metal symbols in alphabetical order, separated by commas.

Thank you

Answer 1

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