Transition Metals Part 2

Question 1

How many common oxidationstates does vanadium have

Answer 1

4

Question 2

When can the different oxidation states of vanadium be seen

Answer 2

When a solution of ammonium vanadate is reduced using zinc in acidic conditions

Question 3

Common oxidation states of vanadium: what colour is VO2 + ion with ON +5

Answer 3

Yellow

Question 4

Common oxidation states of vanadium: what colour is ion VO2+ with ON +4

Answer 4

Blue

Question 5

Common oxidation states of vanadium: what colour is V3+ ion with ON +3

Answer 5

Green

Question 6

Common oxidation states of vanadium: what colour is V2+ ion with ON +2

Answer 6

Violet

Question 7

Half equation reduction VO2 + to VO2+

Answer 7

VO2 + 2H+ + e- > VO2+ + H2O

Question 8

Half equation oxidation of Zn

Answer 8

Zn > Zn2+ + 2e-

Question 9

Overall equation reduction of VO2 + to VO2+ by zinc in acidic conditions

Answer 9

2VO2 + + 4H+ + Xn> 2VO2+ + 2H2O + Zn2+

Question 10

Half equation for reduction of VO2+ to V3+

Answer 10

VO2+ + 2H+ + e- > V3+ + H2O

Question 11

Half equation for oxidation of Zn

Answer 11

Zn > Zn2+ + 2e-

Question 12

Overall equation for reduction of VO2+ to V3+ in acidic conditions

Answer 12

2VO2+ + 4H+ + Zn > 2V3+ + Zn2+ + 2H2O

Question 13

Half equation for reduction of V3+ to V2+

Answer 13

V3+ + e- > V2+

Question 14

Half equation for oxidation of Zn

Answer 14

Zn > Zn2+ + 2e-

Question 15

Overall equation for reduction of V3+ to V2+ by zinc in acidic conditions

Answer 15

2V3+ + Zn > 2V2+ + Zn2+

Question 16

Formula for tollens reagent

Answer 16

[Ag(NH3)2]+

Question 17

What happens to an aldehyde when it’s warmed with tollens reagent

Answer 17

It’s oxidised to a carboxylic acid

Question 18

What happens to the silver ions when tollens is reacted with an aldehyde

Answer 18

Silver ions reduced to silver metal

Question 19

Equation for reduction of tollens reagent

Answer 19

[Ag(NH3)2]+ + e- > Ag + 2NH3

Question 20

Why do ketones give no reaction in tollens test

Answer 20

Can’t be oxidised

Question 21

What is the redox potential of an ion/atom a measure of

Answer 21

How easily it is reduced to a lower oxidation state.

Question 22

Why does a more positive redox potential mean an ion is less stable

Answer 22

More likely to be reduced

Question 23

What is the redox potential the same as standard electrode potential providing

Answer 23

It is measured unde standard conditions in aqueous solution

Question 24

Why are the ligands surrounding the metal ion water in standard electrode potential

Answer 24

Standard electrode potentials are measured in aqueous solution

Question 25

Why will changing the ligand change the value of the redox potential

Answer 25

Other ligands will bond more or less strongly to central mental ion

Question 26

Half equation for reduction of dichromate in acidic conditions

Answer 26

Cr2O72- + 14H+ > 6e- > 2Cr3+ + 2H2O

Question 27

What effect would reducing pH of dichromate have on redox potential

Answer 27

Lower pH > higher [H+] > eqm RHS > more +ve redox potential

Question 28

Half Equation for reduction of manganate

Answer 28

MnO4- + 8H+ + 5e- > Mn2+ + 4H2O