QA Test for Cations

Question 1

White precipitate in NaOH (aq)

Answer 1

Al3+, Pb2+, Zn2+, Ca2+

Question 2

Soluble in excess NaOH (aq)

Answer 2

Al3+, Pb2+, Zn2+

Question 3

Insoluble in excess NaOH (aq)

Answer 3

Ca2+

Question 4

Blue precipitate in NaOH (aq)

Answer 4

Cu2+ [Cu(OH)2]

Question 5

Dirty-green precipitate in NaOH (aq)

Answer 5

Fe2+ [Fe(OH)2] (turns reddish-brown on standing)

Question 6

Reddish-brown precipitate in NaOH (aq)

Answer 6

Fe3+ [Fe(OH)3]

Question 7

No visible change/reaction in NaOH (aq)

Answer 7

Na+, K+, NH4+ (when NH4+ warmed, produces ammonia)

Question 8

White precipitate in NH4 (aq)

Answer 8

Al3+, Pb2+, Zn2+

Question 9

Soluble in NH4 (aq)

Answer 9

Zn2+

Question 10

Insoluble in NH4 (aq)

Answer 10

Al3+, Pb2+ (differentiate by adding aqueous sodium chloride)

Question 11

Blue precipitate in NH4 (aq)

Answer 11

Cu2+ [Cu(OH)2]

Question 12

Deep-blue solution in NH4 (aq)

Answer 12

Cu2+

Question 13

Dirty-green precipitate in NH4 (aq)

Answer 13

Fe2+ [Fe(OH)2] (turns reddish-brown on standing)

Question 14

Reddish-brown precipitate in NH4 (aq)

Answer 14

Fe3+ [Fe(OH)3]

Question 15

No visible change/reaction in NH4 (aq)

Answer 15

Ca2+. Na+, K+, NH4+