Answer to Question #129257 in General Chemistry for Mary

Question

Good day,

A soluble white salt was tested in a Bunsen burner flame, and it gave a brick red colored flame.
When dilute nitric acid and a solution of silver nitrate were added to a solution of the salt, a pale yellow precipitate was observed, which turned slightly grey when left in the sunlight.
Identify the white salt.

Potassium phosphate
Barium sulfate
Calcium iodide
Strontium nitrate
Lead carbonate
Potassium chloride

Answer 1

Barium sulfate and Lead carbonate are insoluble salts. Calcium iodide is a colourless deliquescent solid. Burning potassium chloride produces blue or light violet flame. Strontium nitrate burns with a red flame, but does not produce a yellow precipitate with Silver nitrate. Potassium phosphate, on the other hand, is a white salt soluble in water. Since the precipitate formed by reacting potassium chloride with silver nitrate is white, then the precise answer is potassium phosphate whose precipitate with silver nitrate is yellow. Potassium phosphate definitely should produce brick red flame when burnt using a Bunsen burner.