transition metals

Question 1

[Cu(H2O)6]2+

Answer 1

from CuSO4.5H2O)(s)
pale blue

Question 2

Cu(OH)2(s)

Answer 2

NH3 drop wise to Cu2+(aq)
pale blue precipitate

Question 3

[Cu(NH3)4(H2O)2]2+

Answer 3

excess NH3 to Cu2+
dark blue

Question 4

(CuCl4)2-

Answer 4

excess HCl to Cu2+(aq)
yellow

Question 5

Cu+

Answer 5

reduction of Cu2+ which I-
white precipitate (CuI) and brown I2

Question 6

Cu2+/Cu

Answer 6

Disproportion of Cu+
brown solid (Cu) and blue solution (CuSO4)

Question 7

(CoCl4)2-

Answer 7

from CoCl2.6H2O(s) plus water and excess Hal
blue

Question 8

[Cr(H2O)6]3+

Answer 8

from KCr(SO4)2.12H2O(s)
Pale purple (heat goes to green)
due to impurities common for Cr(III) to appear green in solution

Question 9

Cr(OH)3(s)

Answer 9

NH3 dropwise to Cr3+(aq)
dark green precipitate

Question 10

[Cr(NH3)6]3+

Answer 10

excess NH3 to Cr2+(aq)
purple

Question 11

[Cr(OH)6]3-

Answer 11

excess OH- to Cr(OH)3(s)
dark green

Question 12

(Cr2O7)2-

Answer 12

from K2Cr2O7(s) in 0.1mol dm-3 H2SO4 orange

Question 13

(CrO4)2–

Answer 13

oxidation of Cr3+ with hot alkaline H2O2 yellow

Question 14

[Mn(H2O)6]2+

Answer 14

from MnSO4.4H2O(s)
pale pink

Question 15

Mn(OH)2(s)

Answer 15

NaOH dropwise to Mn2+(aq)
pale brown precipitate

Question 16

[Fe(H2O)6]2+

Answer 16

from FeSO4.7H2O(s)
pale green

Question 17

Fe(OH)2(s)

Answer 17

NaOH dropwise to Fe2+(aq)
dark green precipitate

Question 18

[Fe(H2O)6]3+

Answer 18

from FeCl3.6H2O(s)
yellow

Question 19

Fe(OH)3(s)

Answer 19

NaOH dropwise to Fe3+(aq)
orange-brown precipitate

Question 20

MnO4–/Fe2+ to Mn2+/Fe3+

Answer 20

purple (MnO4–) to pale pink (Mn2+) (in titrations, so dilute that it is practically colourless)

Question 21

I–/Fe3+ to I2/Fe2+

Answer 21

orange brown (Fe3+) to brown (I2)

Question 22

define a transition element

Answer 22

a d block element that forms at least one stable ion with a partially filled d subshell

Question 23

where are the transition elements located in the periodic table

Answer 23

middle block from Ti to Cu

Question 24

2 elements in d block not considered transition elements

Answer 24

scandium and zinc
-scandium only forms Sc3+ ions where d block is empty
- zinc only forms Zn2+ where d orbital is full

Question 25

physical properties of transition elements

Answer 25

• metallic
• high density
• high melting and boiling point
• shiny
• good conductors of heat and electricity

Question 26

what are the chemical properties of transition metals

Answer 26

-coloured compounds/ions in solution
- good catalysts
- form complex ions
-variable oxidation states (take part in many redox reactions)

Question 27

2 main ways in which transition metals act as good catalysts

Answer 27

• provide a surface on which a reaction can take place
• they change oxidation states to form intermediates required for pathways with lower activation energies

Question 28

What is a complex ion

Answer 28

transition metal ion bonded to one or more ligands by coordinate bonds

Question 29

define a ligand

Answer 29

molecule or ion that can donate a pair of electrons to the metal to form a coordinate bond

Question 30

What is a coordinate bond

Answer 30

a bond in which one atom requires both the electrons required for bonding, also known as dative bonding

Question 31

what does coordinate number indicate

Answer 31

number of coordinate bonds formed between the metal ion and its ligands

Question 32

what is a mono/Unidentate ligand
What is a bidentate ligand

Answer 32

-a ligand that forms one(mono)/2(bi) coordinate bond to the central metal ion

Question 33

common monodentate ligands

Answer 33

Cl-,NH3,H2O,CN-

Question 34

what is optical isomerism

Answer 34

non-superimposable mirror images

Question 35

What is cis-plain used for

Answer 35

it is used as an anti-cancer drug
it binds to DNA or fast growing cancer cells and prevents cell division, hence reducing the growth of cancer

Question 36

why is CO toxic

Answer 36

CO coordinately bonds to Fe2+ and bonds more strongly to Fe2+ than O2. so stops O2 from bonding to haemoglobin, so O2 cannot be transported around the body