what test can you use to find potassium ions in an aqueous solution?

Answer 1

If you took the samples to a commercial lab, they would run either atomic absorption (AA) spectrophotometry, ICP-AES spectrophotometry, or ICP-MS spectrometry. If you have low levels like might be found in river or drinking water, you have to do it by one of these instrumental method. Wet methods and flame tests only work at higher levels with clean samples.

Answer 2

1

Answer 3

Potassium Ions

Answer 4

The flame test, First, clean a length of platinum wire in a gas flame by dipping the wire into dilute hydrochloric acid. Next pass the wire through a gas flame. Next, dip the wire into the solution to be tested. Place the wire in the flame. Put a slab of cobalt glass in front of one eye while observing the color. If you see a lilac color, then it is potassium. If the solution contains sodium, then there will be a flare of yellow light. But the cobalt glass will block the sodium yellow, and you will see the lilac of potassium.

Answer 5

Solutions of ions, when mixed with concentrated HCl and heated on a nickel/chromium wire in a flame, cause the flame to change to a color characteristic of the atom. The presence of potassium ion causes a flame to turn pale violet.

Answer 6

Make chlorine water (HCl + bleach) with more HCl than necessary for stoichiometric conversion, add a very small amount of chlorine water to a sample of your aqueous salt. A reddish brown color is indicative of bromine, A violet brown is indicative of iodine. Reactions. 2 HCl + NaOCl ------> NaCl + H2O + Cl2 Cl2 + 2 KBr ----------> 2 KCl + Br2 Cl2 + 2 KI ------------> 2 KCl + I2 Another test would be to take a dilute amount of Ferric Chloride in HCl and add that to a small sample of your salt. No reaction means Bromide A change from yellow to green-violet indicates iodide 2 FeCl3 + 2 KBr -------> NR 2 FeCl3 + 2 KI -------> 2 FeCl2 + 2 KCl + I2

Answer 7

Steve is correct, it is the flame test.

Potassium will not form a precipitate in aqueous solutions!

Answer 8

Lancenigo di Villorba (TV), Italy

I AGREE NOT WITH PRECEEDING ANSWERS.
IN GENERAL, YOUR TROUBLE CANNOT SIMPLY SOLVED.
Potassium compounds can be detected by means of several methods.

FLAME'S TEST
Who preceeds me wrote right in order to execute burner's flame test concerning potassium detection.
You clean a Ni/Cr's metalic wire by passing through burner's flame, you dipp the wire in concentrated hydrochloric acid's solution, hence you put the wire in analyte.
The wire backs in the flame : a violet flame's coloration indicate potassium compounds.
IN PRESENCE OF SODIUM compounds, the latter hide potassium's effects, so you see yellow-bright flame owing to sodium ions but you cannot detect potassium ones. In this case, you need a dark glass to retain luminous radioactions emitted by sodium ions, in this manner you will see violet potassium's flame also in analyte polluted by sodium compounds.

OTHER ESSAYS
I remember you that classical flame's burner test IS NOT LONELY ESSAY to detect potassium compounds in an analyte. THEY EXIST SOME POTASSIUM COMPOUNDS HAVING LOW SOLUBILITY IN AQUEOUS MEDIA.
I remember you also that ammonium ion show a chemical behaviour very analogous to potassium's one.
YOU MUST DESTROY AMMONIUM COMPOUNDS BY MEANS OF PREVIOUS DISSOLUTION OF ANALYTE IN HOT ALKALINE SOLUTIONS.

1st Essay)
In a glass tube you put an amount of analyte and you add some spoons of cobalt sulphate. You dipp this mixture with diluted nitric acid's solution, hence you put the tube in warm-bath conditions. This operation must destroy red fumes which lift up by warm liquid. You chill the liquid in the tube by standing in room's temperature. Now, you add many spoons of sodium acetate to correct pH of solution.
Finally, you add several spoons of sodium nitrite and the tube backs in warm-bath conditions. You may obtain a precipitate constitued by some yellowish crystals, e.g. K3[Co(NO2)6], potassium hexa-nitro-cobaltate(III) also known as Fischer's salt).
If you doubt, you chill the liquid and you add some drops of ethanol.

2nd Essay)
In a glass tube you put an amount of analyte and you add many spoons of sodium acetate. You dipp this mixture with acetic acid's solution.
Finally, you add some spoons of pure tartaric acid or its concentrated aqueous solutions. You let the liquid in the tube by standing in room's temperature.
You may obtain a precipitate constitued by some crystals,
e.g. C4H5O6K, potassium hydrogenotartrate also known as cremotartare.
If you doubt, you chill the liquid and you add some drops of ethanol.

CONCLUSION
In the overwritten I highlight common feature for precipitation of low solubility's potassium compounds.
I remember you that ammonium ions show a very analogous chemical behaviour, so you must destroy these compound by means of hot alkaline solutions.
I remember you that flame's test can distinguish between potassium precipitated and ammonium one.

I hope this helps you.

Answer 9

using the solubility rules mix it with a compound that would form a precipitate with it

Answer 10

Rorschach, good luck.