Cation Tests

Question 1

Ammonium

Answer 1

Aqueous sodium hydroxide: ammonia produced on warming

Question 2

Calcium

Answer 2

Aqueous sodium hydroxide: White ppt, insoluble in excess

Aqueous ammonia: No ppt, or very slightly white ppt

Question 3

Chromium (III)

Answer 3

Aqueous sodium hydroxide: green ppt, soluble in excess

Aqueous ammonia: grey-green ppt, insoluble in excess

Question 4

Copper

Answer 4

Aqueous sodium hydroxide: light blue ppt, insoluble in excess
Aqueous ammonia: light blue ppt, soluble in excess, giving a dark blue solution

Question 5

Iron (II)

Answer 5

Aqueous sodium hydroxide: green ppt, insoluble in excess

Aqueous ammonia: green ppt, insoluble in excess

Question 6

Iron (III)

Answer 6

Aqueous sodium hydroxide: red-brown ppt, insoluble in excess
Aqueous ammonia: red-brown ppt, insoluble in excess

Question 7

Zinc

Answer 7

Aqueous sodium hydroxide: White ppt, soluble in excess giving a colourless solution
Aqueous ammonia: White ppt, soluble in excess giving a colourless solution

Question 8

Define precipitate

Answer 8

A solid that forms when two solutions are mixed

Question 9

Aluminium

Answer 9

Aqueous sodium hydroxide: White ppt, soluble in excess giving a colourless solution
Aqueous ammonia: White ppt, insoluble in excess