Grp 2 Cu²+

Question 1

Give the colours of PbS,CuS,Bi2S3,HgS,CdS

Answer 1

Black,Black,black,black,yellow

Question 2

Which of these are soluble in dil HNO3?

Answer 2

Bi2S3, HgS is insoluble but soluble in aq NH3

Question 3

Cu²+ +KI mention colour too

Answer 3

Cu2I2(white ppt) + I2(g)

Question 4

Can Cu²+ form complex with KI?

Answer 4

No

Question 5

Cu²+ + KCN mention colour too

Answer 5

Cu(CN)2 (yellow ppt)

Question 6

What does Cu(CN)2 further dissociate to give?

Answer 6

CuCN + (CN)2 (cyanogen)

Question 7

CuCN + excess KCN

Answer 7

[Cu(CN)4]³-

Question 8

Cu²+ + KSCN mention colour too

Answer 8

Cu(SCN)2 (black ppt)

Question 9

What does Cu(SCN)2 decompose to give?

Answer 9

CuSCN (white ppt) + (SCN)2

Question 10

CuSCN + excess KSCN

Answer 10

[Cu(SCN)4]³-

Question 11

Cu²+ NH3(aq) mention colour too

Answer 11

Cu(OH)2 (blue ppt)

Question 12

Cu(OH)2 + NH3 excess mention colour too

Answer 12

[Cu(NH3)4]²+ (deep blue)

Question 13

Cu2+ + NaOH mention colour too

Answer 13

Cu(OH)2 (blue ppt)

Question 14

Is Cu(OH)2 amphoteric?

Answer 14

No

Question 15

K4[Fe(CN)6] + Cu²+, mention colour too

Answer 15

Cu2[Fe(CN)6] (chocolate brown)

Question 16

Is Cu2[Fe(CN)6] soluble in dil acids ? Is it soluble in aq NH3?

Answer 16

No, yes

Question 17

Cu2[Fe(CN)6] + NH3

Answer 17

[Cu(NH3)4]²+ + [Fe(CN)6]⁴‐

Question 18

Cu²+ + [Fe(CN)6]³- mention colour too

Answer 18

Cu3[Fe(CN)6]3 (green ppt)