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How can a solution of potassium phosphate be distinguished chemically from a potassium sulfate solution?

Answer 1

Naomi Aronson

Use the ammonium molybdate test.

Warm each solution with dilute nitric acid; then add a solution of ammonium molybdate.

The solution of potassium sulfate will give no reaction.

The solution of potassium phosphate will give a canary yellow precipitate of ammonium molybdate.

The equation is

#"K"_3"PO"_4"(aq)" + 12underbrace(("NH"_4)_2"MoO"_4"(aq)")_color(red)("ammonium molybdate") + "21HNO"_3"(aq)" → underbrace(("NH"_4)_3"PO"_4·"12MoO"_3"(s)")_color(red)("ammonium phosphomolybdate") + "21NH"_4"NO"_3"(aq)" + "12H"_2"O(l)"#

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Answer 2

Axel Alvarado

A solution of potassium phosphate can be distinguished from a potassium sulfate solution through chemical tests. Specifically, adding a solution of barium chloride (BaCl₂) would result in the formation of a white precipitate in the potassium sulfate solution, while no precipitate would form in the potassium phosphate solution. This distinction is due to the insolubility of barium phosphate compared to the soluble barium sulfate.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.