5. Reactions of ions

Question 1

interconversion betweenFe2+ and Fe3+

Fe2+ is oxidised to Fe3+ by which solution?

Answer 1

acidified potassium manganate (VII)

KMnO4(aq)

Question 2

interconversion betweenFe2+ and Fe3+

Fe3+ is reduced to Fe2+ by which ions?

Answer 2

Iodide ions

I-(aq)

Question 3

Interconversion between Cr3+ and Cr2O7 2-
Cr3+ ion in [Cr(OH)6]3- is oxidised to CrO42- by what solution and conditions>
(Cr3+ -> Cr6+)

Answer 3

warming with hydrogen peroxide solution H2O2(aq)

in alkaline conditions

Question 4

Interconversion between Cr3+ and Cr2O7 2-
Cr2O7 2- is reduced to Cr3+ by what solution?
(Cr6+ -> Cr3+)

Answer 4

acidified zinc

Question 5

Reduction of Cu2+ (Cu2+ -> Cu+)

1. Cu2+ is reduced to CuI by which ions?
2. equation

Answer 5

1. Iodide ions I-

2. 2Cu2+(aq) + 4I-(aq) -> 2CuI(s) + I2(aq)

Question 6

Equation for disproportionation of Cu+

Answer 6

2Cu+(aq) -> Cu(s) and Cu2+(aq)

Question 7

identifying transition elements adding NaOH(aq) dropwise

Cu2+ observation

Answer 7

blue precipitate

Question 8

identifying transition elements adding NaOH(aq) dropwise

Fe2+ observation

Answer 8

green precipitate

Question 9

identifying transition elements adding NaOH(aq) dropwise

Fe3+ observation

Answer 9

orange precipitate

Question 10

identifying transition elements adding NaOH(aq) dropwise

Mn2+ observation

Answer 10

pink/buff precipitate

Question 11

identifying transition elements adding NaOH(aq) dropwise

Cr3+ observation

Answer 11

grey-green precipitate

Question 12

Common ligands.
CO3 2- (carbonate)
1. test
2. observation

Answer 12

1. add nitric acid. bubble any gas given off through limewater.
2. lime water turns from clear to cloudy if carbonate present (CO2(g))

Question 13

Common ligands.
CO3 2- (carbonate)
1. test
2. observation

Answer 13

1. add silver nitrate

2. white precipitate

Question 14

Common ligands.
Br- (bromide)
1. test
2. observation

Answer 14

1. add silver nitrate

2. cream precipitate

Question 15

Common ligands.
I- (iodide)
1. test
2. observation

Answer 15

1. add silver nitrate

2. pale yellow precipitate

Question 16

Common ligands.
SO4 2- (sulfate)
1. test
2. observation

Answer 16

1. add barium nitrate Ba(NO3)2 OR barium chloride BaCl2

2. white precipitate

Question 17

Common ligands.
NH4+ (ammonium)
1. test
2. observation

Answer 17

1. add cold NaOH and warm. hold damp red litmus paper over solution
2. red litmus paper turns blue in presence of ammonia.

Question 18

why use HNO3 instead of HCl in the test for carbonates?

Answer 18

HCl would add chloride ions to sample.

can’t tell wether the initial sample contained chloride ions (deffo get white precipitate with silver nitrate)