Transition metals

Question 1

Fe 2+ in aqueous solution

Answer 1

[Fe(H2O)6]2+ green solution

Question 2

Cu 2+ in aqueous solution

Answer 2

[Cu(H2O)6]2+ blue solution

Question 3

Fe 3+ in aqueous solution

Answer 3

[Fe(H2O)6]3+. pale violet solution but appears orange due to hydrolysis to some [Fe(H2O)5(OH)]2+

Question 4

Al 3+ in aqueous solution

Answer 4

[Al(H2O)6]3+ colourless solution

Question 5

Add aqueous NaOH dropwise to Fe2+

Answer 5

[Fe(H2O)4(OH)2] green precipitate (darkens on standing due to oxidation to [Fe(H2O)3(OH)3]

Question 6

Add aqueous NaOH dropwise to Cu 2+

Answer 6

[Cu(H2O)4(OH)2] blue precipitate

Question 7

Add aqueous NaOH dropwise to Fe3+

Answer 7

[Fe(H2O)3(OH)3] brown precipitate

Question 8

Add aqueous NaOH dropwise to Al3+

Answer 8

[Al(H2O)3(OH)3] white precipitate

Question 9

addition of excess aqueous NaOH to Fe2+

Answer 9

no further reaction form when was added dropwise

Question 10

addition of excess aqueous NaOH to Cu2+

Answer 10

no further reaction form when was added dropwise

Question 11

addition of excess aqueous NaOH to Fe3+

Answer 11

no further reaction form when was added dropwise

Question 12

addition of excess aqueous NaOH to Al3+

Answer 12

[Al(H2O)2(OH)4]- re-dissolved to give colourless solution

Question 13

adding aqueous NH3 dropwise to Fe2+

Answer 13

[Fe(H2O)4(OH)2] green precipitate which darkens on standing due to oxidation causing [Fe(H2O)3(OH)3]

Question 14

adding aqueous NH3 dropwise to Cu2+

Answer 14

[Cu(H2O)4(OH)2] blue precipitate

Question 15

adding aqueous NH3 dropwise to Fe3+

Answer 15

[Fe(H2O)3(OH)3] brown precipitate

Question 16

adding aqueous NH3 dropwise to Al3+

Answer 16

[Al(H2O)3(OH)3] white precipitate

Question 17

Adding excess aqueous NH3 to Fe2+

Answer 17

no further reaction form when it was added dropwise

Question 18

Adding excess aqueous NH3 to Cu2+

Answer 18

[Cu(H2O)2(NH3)4]2+ deep blue solution

Question 19

Adding excess aqueous NH3 to Fe3+

Answer 19

no further reaction form when it was added dropwise

Question 20

Adding excess aqueous NH3 to Al3+

Answer 20

no further reaction form when it was added dropwise

Question 21

adding aqueous Na2CO3 to Fe2+

Answer 21

FeCO3 green precipitate

Question 22

adding aqueous Na2CO3 to Cu2+

Answer 22

CuCO3 blue-green precipitate

Question 23

adding aqueous Na2CO3 to Fe3+

Answer 23

[Fe(H2O)3(OH)3] brown precipitate and bubbles of CO2 gas

Question 24

adding aqueous Na2CO3 to Al3+

Answer 24

[Al(H2O)3(OH)3] white precipitate and bubbles of CO2 gas

Question 25

adding concentrated HCl to Fe2+

Answer 25

[FeCl4]2- yellow solution

Question 26

adding concentrated HCl to Cu2+

Answer 26

[CuCl4]2-green solution

Question 27

adding concentrated HCl to Fe3+

Answer 27

[FeCl4]-yellow solution

Question 28

adding concentrated HCl to Al3+

Answer 28

[AlCl4]- colourless solution

Question 29

reaction between iodide ions and S2O8 2- catalysed by Fe

Answer 29

S2O8 2- + 2Fe2+ - --> 2 SO4 + 2Fe3+ 2I- + 2Fe3+ - --> I2 + 2Fe2+ all arrows are reversible reactions can occur either way round which is why Fe2+ or Fe3+ can be the catalyst overall: 2 I- + S2O8 2- --> I2 + 2 SO4 2-

Question 30

contact process

Answer 30

-catalysed by V2O5 V2O5 + SO2 --> V2O4 + SO3 V2O4 + 0.5O2 --> V2O5 overall: 2 SO2 + O2 --> 2 SO3

Question 31

colours of vanadium ions oxidation state = +5

Answer 31

VO2 + yellow

Question 32

colours of vanadium ions oxidation state = +4

Answer 32

VO 2+ blue

Question 33

colours of vanadium ions oxidation state = 3+

Answer 33

V 3+ green

Question 34

colours of vanadium ions oxidation state = 2+

Answer 34

V 2+ violet

Question 35

haber process

Answer 35

3 H2 + N2 --> 2 NH3 reversible reaction arrow

Question 36

reaction of ethanedioate ions and manganate ions

Answer 36

2 MnO4- + 16H+ + 5C2O42- --> 2 Mn2+ + 8 H20 + 10 CO2 catalysed by Mn2+ ions

Question 37

reaction of manganate ions and iron ions

Answer 37

MnO4- + 8 H+ + 5 Fe 2+ --> Mn2+ + 4 H2O + 5 Fe 3+

Question 38

role of iron as a catalyst in the haber process

Answer 38

Heterogeneous catalysts: -heterogeneous catalyst which is in a different physical state to reactants -catalyst speeds up rate of reaction by lowering activation energy by providing an alternative reaction pathway (left unchanged) How to works on the haber process: -hydrogen and nitrogen adsorb onto the surface (active sites) of the iron -the bonds weaken and the reaction takes place -the products desorb and leave the surface of the iron How to increase/what affects efficiency: -large surface area by using a powder or small pellets (or support medium/mesh) -the catalyst is poisoned as the sulfur binds to the catalyst -the active sites are blocked

Question 39

what is an autocatalyst

Answer 39

a type of homogenous catalyst where the product is also a catalyst

Question 40

how do heterogenous catalysts work

Answer 40

-different physical state to the reactants -adsorbed onto the molecules active site and weakens the covalent bonds so reaction can occur more easily and rate is increased -they can be poisoned by impurities which blocks the active site and prevents adsorption (so the bonds remain strong) -reaction impurities increase chemical production costs as the catalyst has to be replaced or cleaned regularly -rate can be increased by using a powder as increases surface area

Question 41

why might there be impurities in the heterogeneous catalyst iron in the haber process

Answer 41

-the H2 is made from methane which contains sulfur impurities -the sulfur will adsorb to the surface forming iron sulfide -this makes the catalyst less efficient so needs to be cleaned or replaced often which is expensive

Question 42

how do homogenous catalysts work

Answer 42

-same physical state as the reactants -the catalyst combines the reactants to produce a reactive intermediate -this changes the reaction pathway as the activation energy is initially high as two negative ions repel , so the enthalpy change for the formation of the intermediate is lower than the original reaction, so it is more feasible

Question 43

oxidation of iodide ions catalysed by the homogenous catalyst iron

Answer 43

S2O8 2- + 2Fe 2+ --> 2Fe 3+ + 2SO4 -the intermediate Fe£+ produced catalyses 2I- + 2Fe 3+ --> 2 Fe 2+ + I2

Question 44

reduction of VO2 (+) to V (3+) by Zn charges in ()

Answer 44

2 VO2(+) + Zn + 4H(+) --> 2VO(2+) + Zn(2+) + 2H2O yellow --> blue 2VO(2+ )+ Zn + 4H(+) --> 2V (3+) + Zn(2+) + 2H20 Blue --> green 2V(3+) + Zn --> 2V(2+) + Zn(2+) green --> violet