Cation tests

Question 1

Aluminum, Al3+

Answer 1

Effect in aq sodium hydroxide-
White ppt
Soluble in excess
giving a colorless solution

Effect in aq ammonia-
White ppt
Insoluble in excess

Question 2

Ammonium, NH4+

Answer 2

Effect on aq sodium hydroxide-

Ammonia produced on warming

Question 3

Calcium, Ca2+

Answer 3

Effect on aq sodium hydroxide-
White ppt
Insoluble in excess

Effect in aq ammonia-
No ppt, or very slight white ppt

Question 4

Chromium(III), Cr3+

Answer 4

Effect on aq sodium hydroxide-
Green ppt
Soluble in excess

Effect in aq ammonia-
Grey-green ppt
Insoluble in excess

Question 5

Copper(II), Cu2+

Answer 5

Effect on aq sodium hydroxide-
Light blue ppt
Insoluble in excess

Effect in aq ammonia-
Light blue ppt
soluble in excess
giving a dark blue solution

Question 6

Iron(II), Fe2+

Answer 6

Effect on aq sodium hydroxide-
Green ppt
Insoluble in excess
The ppt changes color on the surface to brown (on standing)

Effect in aq ammonia-
Green ppt
Insoluble in excess
The ppt changes color on the surface to brown (on standing)

Question 7

Zinc, Zn2+

Answer 7

Effect on aq sodium hydroxide-
White ppt
Soluble in excess
Giving a colorless solution

Effect in aq ammonia-
White ppt
Soluble in excess
Giving a colorless solution

Question 8

Iron(III), Fe3+

Answer 8

Effect on aq sodium hydroxide-
Red-brown ppt
Insoluble in excess

Effect in aq ammonia-
Red-brown ppt
Insoluble in excess