Grp 4 Co²+

Question 1

Mention the group 4 sulphides and their colours

Answer 1

CoS and NiS are black, ZnS is white and MnS is pale pink

Question 2

Is CoS soluble in aqua regia?

Answer 2

Yes

Question 3

Co²+ + NaOH———NO3—->
mention colour too

Answer 3

Co(OH)NO3 (basic blue)

Question 4

Co(OH)NO3 + excess NaOH
mention colour too

Answer 4

Co(OH)2 (pink ppt)

Question 5

Co(OH)2 + +aq NH3 (excess)
mention colour too

Answer 5

[Co(NH3)6]²+ (yellowish brown)

Question 6

[Co(NH3)6]²+ in the presence of air gives? mention colour too

Answer 6

[Co(NH3)6]³+ (red brown)

Question 7

Co²+ + CN- mention colour too

Answer 7

Co(CN)2 (reddish brown)

Question 8

Co(CN)2 + excess KCN , what does it give in the presence of air?

Answer 8

[Co(CN)6]⁴- (brown) in the presence of air gives [Co(CN)6]³- (yellow)

Question 9

Co²+ + NO2- + H+ + 3K+ mention colour too

Answer 9

K3[Co(NO2)6] (yellow) + NO

Question 10

NH4SCN + Co²+ mention colour too

Answer 10

[Co(SCN)4]²- (blue colouration)