Answer to Question #72003 in General Chemistry for Abdulai Sesay

Question

a salt have potassium chloride, explain the preliminary and confirmatory test for cation and anion

Answer 1

Solution:

For chloride anion:

Preliminary test is: Salt + concentrated H2SO4.
There is next response if anion present: colorless white pungent fumes (HCl); intensify when glass rod dipped in NH4OH is brought near mouth of test tube
Confirmatory test
1. Silver nitrate test: Salt (aq) + AgNO3 = white precipitate soluble in NH4OH
2. Chromyl chloride test: Salt + K2Cr2O7 (s) + 2-3 drops concentrated H2SO4 = orange / red fumes of chromyl chloride
1. Vapours + NaOH (aq) = yellow solution
2. Yellow solution + acetic acid + lead acetate sol = yellow precipitate

For potassium cation:

Preliminary test: volatile chlorides of alkali metals dye the colorless flame of the burner in a certain color. Potassium gives a red color (viewing through two layers of blue glass).
Confirmatory test:
Salt (aq) + Na3Co(NO2)6 (aq) = yellow precipitate of K2Na[Co(NO2)6]·H2O