Ion test

Question 1

CO3^2-

Answer 1

Add HNO3 (aq)

Effervescence of CO2
CO3^2-(aq)+ 2H+(aq)-> CO2(aq) + H2O(l)

Question 2

SO4^2-

Answer 2

Add Ba^2+(aq)

White precipitate of BaSO4
Ba^2+(aq) + SO4^2-(aq) -> BaSO4(s)

Question 3

Cl-

Answer 3

Add Ag^+(aq)

White precipitate of AgCl
If Cl- ions present, soluble in dilute NH3 (aq)
Ag+(aq) +Cl-(aq) -> AgCl(aq)

Question 4

Br-

Answer 4

Add Ag^+ (aq)

Cream precipitate of AgBr
If Br- ions present, soluble in conc NH3
Ag+(aq) + Br-(aq) -> AgBr(s)

Question 5

I-

Answer 5

Add Ag^+ (aq)

Yellow precipitate of AgI
If I- present, insoluble in conc NH3(aq)
Ag+(aq) + I-(aq) -> AgI (s)

Question 6

NH4^+

Answer 6

Add OH-(aq) and heat gently

Damp red pH indicator will turn blue if NH3 is evolved
NH4^+(aq) + OH-(aq) -> NH3(g) +H2O(l)

Question 7

Cu^2+

Answer 7

Add I-(aq)

White precipitste of CuI, if Cu^2+ present
I2(s) is a brown solution
2Cu^2+(aq) +4I-(aq) -> 2CuI(aq) + I2(s)

Question 8

Fe^2+

Answer 8

Add OH-(aq)

Pale green precipitate of Fe(OH)2 which turns orange-brown in air
Fe^2+(aq) +2OH-(aq) -> Fe(OH)2 (s)

Question 9

Fe^3+

Answer 9

Add OH-(aq)

Orange-brown precipitate of Fe(OH)3
Fe^3+(aq) +3OH-(aq) -> Fe(OH)3 (s)

Question 10

Mn^2+

Answer 10

Add OH-(aq)

Light brown precipitate of Mn(OH)2 and darkens in air
Mn^2+(aq) +2OH-(aq) -> Mn(OH)2 (s)

Question 11

Cr^3+

Answer 11

Add OH-(aq)

Green precipitate of Cr(OH)3 (s), soluble in excess NaOH forming dark green solutio n
Cr^3+(aq) +3OH-(aq) -> Cr(OH)3 (s)
Cr(OH)3(s) +3OH-(aq) -> [Cr(OH)6]3-(aq)