Transition Metal Colours

Question 1

V²⁺ colour

Answer 1

Violet

Question 2

V³⁺ colour

Answer 2

Green

Question 3

VO²⁺ colour

Answer 3

Blue

Question 4

VO₂⁺ colour

Answer 4

Yellow

Question 5

Cr³⁺ colour

Answer 5

Green

Question 6

Cr2O7^2- colour

Answer 6

Orange

Question 7

Mn²⁺ colour

Answer 7

Pale pink

Question 8

MnO4^2- colour and name

Answer 8

Green - manganate

Question 9

Fe²⁺ colour

Answer 9

Pale green

Question 10

Fe³⁺

Answer 10

Yellow

Question 11

MnO4^- colour and name

Answer 11

Purple - permanganate

Question 12

Co²⁺ Colour

Answer 12

Pink

Question 13

Cu²⁺ Colour

Answer 13

Blue

Question 14

CrO4^2- colour

Answer 14

Yellow

Question 15

Cr²⁺ colour

Answer 15

Blue

Question 16

What is used to oxidise Cr³⁺ to chromate ions

Answer 16

Hydrogen peroxide in alkaline solution

Question 17

What is the equilibrium between Chromate and dichromate and therefore which is favoured in acidic conditions

Answer 17

2CrO4^2- + 2H⁺ <—> Cr2O7^2- + H2O

Dichromate is favoured in acid

Question 18

What does amphoteric mean

Answer 18

Acts as an acid and a base

Question 19

What is special about [Cr(H2O)3(OH)3]

Answer 19

It is amphoteric (solid and forms a green precipitate)

Question 20

What happens when you add a base to [Cr(H2O)3(OH)3]

Answer 20

It forms [Cr(OH)6]3- which is a green solution

Question 21

What happens when you add an acid to [Cr(H2O)3(OH)3]

Answer 21

Chromium hexaaqua complex forms

Question 22

Are heqaaqua complex reactions with OH- examples of ligand substitution

Answer 22

No it is an acid base reaction

Question 23

Whats used to reduce dichromate ions to Cr3+ and 2+

Answer 23

Zinc in acidic conditions

Question 24

What is the difference between the reaction with Copper and cobalt hexaaqua complex’s with excess ammonia

Answer 24

Copper only partially substitutes

Question 25

Cobalt complex in Chlorine colour change

Answer 25

Pink to blue

Question 26

Copper Complex in Chlorine colour change

Answer 26

Blue to yellow

Question 27

What is the chelate effect

Answer 27

increase in the stability of a compound when ligand substitution results in increasing entropy

Question 28

Cr3+ Cu2+ Fe2+ Fe3+ Co2+ Colour in some OH- or NH3

Answer 28

Green Pale blue ppt Green ppt Brown ppt Blue ppt

Question 29

Cr3+ Cu2+ Fe2+ Fe3+ Co2+ Colour in excess NH3

Answer 29

Purple Dark Blue No change No change Yellow

Question 30

What is the contact process

Answer 30

An industrial method of making sulfuric acid using vanadium (V) V2O5 catalyst

Question 31

How is V2O5 involved in the contact process Include 2 equations and an overall equation

Answer 31

Catalyses the reaction of SO2 to SO3 acting as a heterogeneous catalyst V2O5 + SO2 —> V2O4 + SO3 V2O4 + 1/2O2 —> V2O5 2SO2 + O2 —> 2SO3

Question 32

3 transition metals in catalytic converters and the reaction they catalyse

Answer 32

Rhodium, platinum and palladium 2CO + 2NO —> 2CO2 + N2

Question 33

What is catalytic poisoning

Answer 33

When using heterogeneous catalysts impurities can bind to the surface and block the active sites. This reduces area of the catalysts for reactants to adsorb to which slows down the reaction

Question 34

Risks of transition metals catalysts (Copper and Manganese) (2)

Answer 34

Copper can cause liver damage and build up in the body. Manganese exposure can result in psychiatric issues

Question 35

Autocatalysis example equation

Answer 35

5C2O4^2- + 2MnO4^- + 16H+ —> 2Mn2+ + 8H2O + 10CO2 Then Mn2+ acts as a catalyst MnO4^- + 8H+ + 4Mn2+ —> 5Mn3+ + 4H2O 2Mn3+ + C2O4^2- —> 2Mn2+ + 2CO2

Question 36

What reaction does iron catalyse and why is a catalyst used Give two equations that show iron acting as a catalyst

Answer 36

Iodine + persulfate reaction. Iron is used as negative ions repel 2I- + S2O8^2- —-> I2 + 2SO4^2- 1. S2O8^2- + 2Fe2+ —> 2Fe3+ + 2SO4^2- 2. 2I- + 2Fe3+ —> Fe2+ + I2

Question 37

What is autocatalysis

Answer 37

The product of a reaction catalyses the reaction