Task

Chemical analysis. A solution brought to the laboratory is thought to contain barium, iron(III), copper(II) and ammonium nitrates. Adding excess dilute sulfuric acid to 100 mL of it gave 2.33 g of a white crystalline precipitate insoluble in acids. Excess ammonia solution was added to one portion of the filtrate; other portions were tested with separate reagents. 1) Write the test for the barium ion in molecular and net ionic form, explain why insolubility of the precipitate in acids matters, and calculate the molar concentration of Ba²⁺. 2) Write the tests for Fe³⁺ with two reagents (potassium thiocyanate and potassium hexacyanoferrate(II)) and state the visible signs. 3) Explain with equations and observations how excess ammonia solution separates Fe³⁺ from Cu²⁺. 4) Write the test for NH₄⁺ and explain why it must be detected in a separate portion of the original solution rather than in the filtrate after ammonia was added. For every part, show the method (reaction equations, formulas, reasoning) and all calculations step by step.