Tests for aqueous cation

Question 1

ammonium (NH4+)

Answer 1

effect of aqueous sodium hydroxide:
- ammonia produced on warming

Question 2

calcium (Ca2+)

Answer 2

effect of aqueous sodium hydroxide:
white ppt., insoluble in excess

effect of aqueous ammonia:
no ppt. or very slight white ppt.

Question 3

copper(II) (Cu2+)

Answer 3

effect of aqueous sodium hydroxide:
light blue ppt., insoluble in excess

effect of aqueous ammonia:
light blue ppt., soluble in excess, giving a dark blue solution

Question 4

iron(II) (Fe2+)

Answer 4

effect of aqueous sodium hydroxide:
green ppt., insoluble in excess

effect of aqueous ammonia:
green ppt., insoluble in excess

Question 5

iron(III) (Fe3+)

Answer 5

effect of aqueous sodium hydroxide:
red-brown ppt., insoluble in excess

effect of aqueous ammonia:
red-brown ppt., insoluble in excess

Question 6

zinc (Zn2+)

Answer 6

effect of aqueous sodium hydroxide:
white ppt., soluble in excess, giving a
colourless solution

effect of aqueous ammonia:
white ppt., soluble in excess, giving a
colourless solution

Question 7

Aluminium (Al3+)

Answer 7

effect of aqueous sodium hydroxide:
white ppt, soluble in excess

effect of aqueous ammonia:
white ppt, insoluble in excess

Question 8

Barium (Ba2+)

Answer 8

effect of aqueous sodium hydroxide:
faint white ppt. is nearly always observed unless reagents are pure

effect of aqueous ammonia:
no ppt.

Question 9

magnesium (Mg 2+(aq))

Answer 9

for both:
white ppt.
insoluble in excess