Tests for ions

Question 1

What are the flame colours for the group 2 metal ions?

Answer 1

Ca2+ - orange/red
Sr2+ - red
Ba2+ - green

Question 2

How would you test for ammonium ions?

Answer 2

Add dilute sodium hydroxide to the unknown solution and gently warm
NH4+ (aq) + OH- (aq) –> NH3 (g) + H2O

Result: ammonia gas is formed which will turn damp piece of red litmus blue

Question 3

How would you test for sulfate ions?

Answer 3

Add dilute hydrochloric acid and barium hydroxide
SO4 2- + Ba 2+ –> BaSO4

Result: a white ppt of barium sulfate formed

Question 4

How would you test for hydroxide ions?

Answer 4

Dip a piece of red litmus paper into solution

Result: will turn blue

Question 5

How do you test for halide ions?

Answer 5

Add dilute nitric acid and silver nitrate solution

Result: precipitate formed. White = Cl- , cream = Br- , yellow = I-

Silver chloride will dissolve in NH3
AgCl (s) + 2NH3 –> Ag(NH3)2+ + Cl-

Question 6

How would you test for carbonate ions?

Answer 6

Add dilute hydrochloric acid to the solution

Result: effervescence caused by CO2. Gas can be tested by bubbling through limewater which will turn milky