Transition Metals left over

Question 1

Give some examples of transition metal catalysts and the process/reactions they catalyse? (3)

Answer 1

Iron - Haber Process
Vanadium (V) oxide - Contact Process
MnO2 - decomposition of H2O2

Question 2

What affects the colour of a TM compound?

Answer 2

ΔE affects the frequency of photons absorbed, so determines the colour of light reflected. ΔE changes with oxidation state of TM, co-ordination number, ligand identity and complex shape.

Question 3

Oxidation number of V in VO2^+

Answer 3

5+

Question 4

Colour of VO2^+

Answer 4

yellow

Question 5

oxidation number of V in VO^2+

Answer 5

4+

Question 6

colour of VO^2+

Answer 6

blue

Question 7

Oxidation number of V^3+

Answer 7

3+

Question 8

colour of V^3+

Answer 8

green

Question 9

oxidation number of V^2+

Answer 9

2+

Question 10

colour of V^2+

Answer 10

violet

Question 11

What can you use to reduce vanadium

Answer 11

zinc

Question 12

Why can TMs have variable oxidation states?

Answer 12

they have partially filled d-orbitals so can lose 4s and 3d e-s

Question 13

Tollens’ reagent molecular formula

Answer 13

[Ag(NH3)2]+

Question 14

What is the half equation for the reduction of MnO4^-

Answer 14

MnO4^- + 8H+ 5e- -> Mn^2+ + H2O

Question 15

What colour is MnO4^- ?

Answer 15

deep purple

Question 16

What colour is Mn^2+ ?

Answer 16

pink

Question 17

What colour is Cr2O7^2- ?

Answer 17

orange

Question 18

What colour is Cr^3+ ?

Answer 18

green

Question 19

Half equation for the oxidation of Cr2O7^2-

Answer 19

Cr2O7^2- + 14H+ + 6e- -> 2Cr^3+ + 7H2O

Question 20

Half equation of the oxidation of Fe^2+

Answer 20

Fe^2+ -> Fe^3+ + e-

Question 21

Half equation of oxidation of C2O4^2-

Answer 21

C2O4^2- -> 2CO2 + 2e-

Question 22

Define heterogenous catalayst.

Answer 22

a catalyst in a different phase to the reactants

Question 23

What type of catalyst is iron?

Answer 23

heterogenous

Question 24

What type of catalyst is V2O5?

Answer 24

heterogenous

Question 25

Define catalyst.

Answer 25

a substance that increases RoR of a reaction by lowering the Ea and providing an alternative reaction pathway and remains unchanged.

Question 26

How do heterogenous catalysts work?

Answer 26

reactants adsorb to the catalyst's surface at active site. This weakens the bonds with the reactants, holds reactants close together on the surface and/or in the correct orientation to react. Once the reaction has occurred, reactants desorb from the active sites.

Question 27

What properties do catalysts need to be good?

Answer 27

- can't adsorb too strongly = products will not desorb - can't adsorb too weakly = desorb too quickly

Question 28

Steps of the contact process.

Answer 28

1. V2O5 + SO2 -> V2O4 + SO3 2. V2O4 + 1/2 O2 -> V2O5 OVERALL: SO2 + 1/2 O2 -> SO3

Question 29

Define homogenous catalyst.

Answer 29

one that is in the same phase the reactants

Question 30

How do homogenous catalysts work?

Answer 30

form intermediates to give a different pathway to lower Ea

Question 31

What is the reaction between I- and S2O8^2- ?

Answer 31

2I- + S2O8^2- -> I2 + 2SO4^2-

Question 32

How does iron catalyse the reaction between I- and S2O8^2- ?

Answer 32

1. 2Fe^2+ + S2O8^2- -> 2Fe^3+ + 2SO4^2- 2. 2Fe^3+ + 2I- -> 2Fe2+ + I2