Transition Metals

Question 1

What’s a transition metal? (2)

Answer 1

• Forms at least one stable ion (1)
• With an incomplete d-subshell (1)

Question 2

Which elements aren’t transition metals? (3)

Answer 2

• Scandium and Zinc (1)
• Both form one stable ion of Zn2+ and Sc3+ (1)
• Sc3+ has an empty d-subshell and Zn2+ has a full
  d-subshell (1)

Question 3

What are 3 properties of transition metals? (3)

Answer 3

• Form colored ions (1)
• Have variable oxidation states (1)
• Good catalysts (1)

Question 4

What are the colored ions and oxidation states of vanadium? (4)

Answer 4

+2 = V 2+ → Violet (1)
+3 = V 3+ → Green (1)
+4 = VO 2+ → Blue (1)
+5 = VO2 + → Yellow (1)

Question 5

What are the colored ions and oxidation states of chromium? (2)

Answer 5

+3 = Cr 3+ → Green/Violet (1)
+6 = Cr2O7 2- → Orange (1)

Question 6

What are the colored ions and oxidation states of manganese? (3)

Answer 6

+2 = Mn 2+ → Pale pink (1)
+6 = MnO4 2- → Green (1)
+7 = MnO4 - → Purple (1)

Question 7

What are the colored ions and oxidation states of iron? (2)

Answer 7

+2 = F2+ → Pale Green (1)
+3 = F3+ → Yellow (1)

Question 8

What are the colored ions and oxidation states of cobalt, nickel and copper? (3)

Answer 8

All are +2:

Co 2+ → Pink (1)
Ni 2+ → Green (1)
Cu 2+ → Blue (1)

Question 9

What are the colored ions and oxidation states of Titanium? (2)

Answer 9

+2 = Ti2+ → Violet (1)
+3 = Ti3+ → Purple (1)

Question 10

Why do transition metals have variable oxidation states? (2)

Answer 10

• Valence electrons sit between 4s and 3d subshell (1)
• electrons are gained and lost using similar amounts
  of energy (1)

Question 11

What is a complex ion? (1)

Answer 11

• Central transition metal surrounded by ligands bonded by
  coordinate bonds (1)

Question 12

What are the types of ligands? (4)

Answer 12

• Monodentate ligands form one coordinate bonds with one lone
  pair (1)
• Bidentate ligands form two coordinate bonds with two lone pairs (1)
• Multidentate ligands have more than one coordinate bond (1)
  • E.G. EDTA4- forms 6 coordinate bonds (1)

Question 13

What is the complex shape with a coordinate number of 6 + example? (3)

Answer 13

• Octahedral with bond angles of 90° (1)
• Co[(H20)6]2+ (1)
• H2O :→ AND ←: OH2 pointing towards central Co metal (1)

Question 14

How do you find the oxidation state of a transition metal in a complex ion? (1)

Answer 14

• Overall charge of the complex ion minus the total charge of the
  ligands (1)

Question 15

What is the effect of carbon monoxide on haemoglobin complex? (2)

Answer 15

• CO ligand replaces the H2O ligand (1)
• Bonded strongly so it isn’t replaced by oxygen resulting in oxygen
  starvation (1)

Question 16

What complex ions show optical isomerism? (2)

Answer 16

• Octahedral complexes with 3 bidentate ligands (1)
• When they are non superimposable mirror images (1)

Question 17

What complex ions shows cis-trans isomerism? (2)

Answer 17

• Octahedral complexes with 4 of the same ligand type and 2 of
  different ligand type (1)
• Trans isomer is when ligands are opposite each other while cis is
  when they’re adjacent (1)

Question 18

How is a color produced from a complex ion? (3)

Answer 18

• 3d subshell splits when ligands bonds with the central metal ion (1)
• Frequency of light is absorbed based energy gap ΔE (1)
• Complementary colour of absorbed light is observed (1)

Question 19

Why would a complex ion be colorless? (2)

Answer 19

• Full or empty 3d subshell (1)
• No electrons can move to a higher energy level (1)

Question 20

What affects ΔE and therefore colour? (2)

Answer 20

• Type of ligand (1)
• Central metal ion (1)

Question 21

What does redox potential tell you? (3)

Answer 21

• More positive means it’s a less stable ion (1)
• More likely to be reduced (1)

Question 22

What is meant by amphoteric chromium hyrdoxides? (3)

Answer 22

• Can act as an acid or a base (1)

[Cr(H20)3(OH)3]s + 3H+ → [Cr(H2O)6]3+ (aq)
[Cr(H20)3(OH)3]s + OH- → [Cr(OH)6]3- (aq) + 3H2O (l)

Question 23

What are the colours of ampthoteric chromium hydroxide? (2)

Answer 23

Gray green solid forms green solution (1)

Question 24

What happens when you add ammonia to Cr(H2O)3(OH)3 ? (3)

Answer 24

• Ligand exchange reaction (1)
• [Cr(NH3)6]3+ produced (1)
• Gray Green solid to purple solution (1)

Question 25

How is the complex chromium ethanoate produced? (4)

Answer 25

- Acidified sodium dichromate is reduced using zinc forming Cr3+ then Cr2+ ions (1) - Goes from orange solution to green solution to blue solution (1) - Sodium ethanoate reacts with Cr2+ to produce [Cr(CH3COO)4(H2O)2] (1) - Goes from blue to red precipitate (1)

Question 26

What is a requirement when making chromium complexes? (2)

Answer 26

- Nitrogen atmosphere for inert conditions (1) - Cr2+ are easily oxidised back to Cr3+ (1)

Question 27

What happens when there is a ligand substitution between water and ammonia? (2)

Answer 27

- Complex shape remains octahedral (1) - Similar sizes ligands with same charge (1)

Question 28

What happens when [Co(H2O)6]2+ reacts with 6NH3? (2)

Answer 28

- Ligand substitution = [Co(NH3)6]2+ (aq) + 6H2O (1) - Pink solution to straw solution (1)

Question 29

What happens when [Cu(H2O)6]2+ reacts with excess ammonia? (2)

Answer 29

- Partial Ligand substitution = [Cu(NH3)4(H2O)2]2+ + 4H2O (1) - Blue solution to Dark Blue solution (1)

Question 30

What happens when there is a ligand substitution between water and chlorine? (3)

Answer 30

- Changes the shape from octahedral to tetrahedral (1) - Coordination number changes from 6 to 4 (1) - Chlorine is a larger ligand with a negative charge (1)

Question 31

What is the reaction and colour change of ligand substitution of chlorine? (3)

Answer 31

[X(H2O)6]2+ (aq) + 4Cl- (aq) → [XCl4]2- + 6H2O (l) Cobalt = Pink to Blue (1) Copper = Blue to Yellow (1)

Question 32

What happens when ligands are exchanged with CN- or bidentate ligands? (2)

Answer 32

- Form stronger bonds than H2O (1) - Reaction is harder to reverse (1)

Question 33

What is the chelate effect? (3)

Answer 33

- Substituting monodentate ligands with bidentate increases solutions particles (1) - Increase in entropy meaning reactions is likely to happen (1) - Difficult to reverse as it would decrease entropy (1)

Question 34

Why would the reaction of ions have a high activation energy? (1)

Answer 34

- The 2 negative ions repel each other (1)

Question 35

How does Fe2+ catalyse the reaction of iodine and peroxodisulfate ions? (3)

Answer 35

- Iron has variable oxidation states (1) 2Fe2+ + S2O8 2- → 2Fe3+ + 2SO4 2- (1) 2Fe3+ + 2I- → 2Fe2+ + I2 (1)

Question 36

How do catalytic convertors work? (3)

Answer 36

- Adsorption of CO/NO - Weakening of bonds (1) - Desorption of CO2 and N2 will release products (1)