Y13 Transition metals

Question 1

d-block element definition

Answer 1

Highest energy electron is in the d subshell

Question 2

Transition metal definition

Answer 2

A d-block element that forms at least one ion with a partially full d subshell

Question 3

What are the electron configurations for Cr and Cu (different to other d-block elements)?

Answer 3

Cr: 4s1 3d5
Cu: 4s1 3d10

Question 4

Why are Sc and Zn d-block elements but not transition metals?

Answer 4

Zn: Only ion formed by Zn is Zn2+ which has a full 3d subshell
Sc: Only ion formed by Sc is Sc3+ which as an empty 3d subshell

Question 5

What is the systematic name of FeO?

Answer 5

Iron (II) oxide

Question 6

What are the 4 catalysts for the Haber process, contact process, hydrogenation of an alkene, and decomposition of H2O2?

Answer 6

Haber process: iron
Contact process: vanadium (V) oxide
Hydrogenation of an alkene: nickel
Decomposition of H2O2: manganese (IV) oxide

Question 7

What are the colours of transition metal ions in solution?

Answer 7

Cu2+: blue

Fe2+: pale green

Fe3+: orange-brown

Mn2+: pale pink

Cr3+: violet

Question 8

What are the observations of transition metals on addition of NaOH?

Answer 8

Cu2+: blue ppt.

Fe2+: green ppt.

Fe3+: orange-brown ppt.

Mn2+: light brown ppt.

Cr3+: green ppt.

Question 9

What is the equation for the addition of NaOH to Cu2+?

Answer 9

Cu2+(aq) + 2OH-(aq) –> Cu(OH)2(s)

Question 10

What are the further changes on addition of NaOH?

Answer 10

Fe2+: green ppt. –> orange-brown ppt.

Cr3+: green ppt. –> green solution

Question 11

Write the complex ion of Fe3+ in solution

Answer 11

[Fe(H2O)6]3+

Question 12

Complex ion definition

Answer 12

Central metal ion surrounded by ligands

Question 13

Ligand definition

Answer 13

Molecule or ion that donates a lone pair of electrons to a central metal ion, forming a coordinate bond

Question 14

What are the steps to drawing a complex ion?

Answer 14

1. Central metal ion
2. Bonds (3D)
3. Atom in ligand donating e- pair
4. Rest of ligand
5. Brackets and charge

Question 15

Monodentate ligand definition

Answer 15

Donates one lone pair of e- to the central metal ion to form one coordinate bond

Question 16

Bidentate ligand definition

Answer 16

Donates 2 lone pairs of e- to the central metal ion to form 2 coordinate bonds

Question 17

How can NH2CH2CH2NH2 act as a bidentate ligand?

Answer 17

Each nitrogen has a lone pair of e- which can be donated to the central metal ion to form 2 coordinate bonds

Question 18

Stereoisomerism definition

Answer 18

Same molecular and structural formula but a different arrangement of atoms in the space

Question 19

What bond angles will the ligands have in cis and trans isomers?

Answer 19

Cis: 90°
Trans: 180°

Question 20

What is the importance of cis-platin?

Answer 20

Drug used in chemotherapy as an anti-cancer drug by binding to cancerous DNA and preventing DNA replication - trans isomer not as effective

Question 21

Optical isomerism definition

Answer 21

Form of stereoisomerism in which the 2 isomers are non-superimposable mirror images of each other

Question 22

When can optical isomerism occur?

Answer 22

1. 3 molecules/ions of a bidentate ligand
2. 2 bidentate ligands and 1 monodentate ligand

Question 23

What is the observation when excess NH3 is added to [Cu(H2O)6]2+?

Answer 23

Blue solution to deep blue solution

Question 24

What is the observation when excess NH3 is added to [Cr(H2O)6]3+?

Answer 24

Green ppt. to purple solution

Question 25

How does ligand substitution allow haemoglobin transport O2 in the blood?

Answer 25

O2 binds to Fe2+ via coordinate bonds and when required, is substituted for CO2/H2O

Question 26

Why is CO toxic?

Answer 26

CO and O2 can both form coordinate bonds with Fe2+ but CO forms stronger coordinate bond with Fe2+ than O2. CO substitutes O2 and this coordinate bond is irreversible so it renders the haemoglobin useless

Question 27

Ligand substitution

Answer 27

One ligand in a complex ion is substituted by a different type of ligand

Question 28

What is the observation when concentrated HCl is added to [Cu(H2O)6]2+ to form [Cu(Cl)4]2-?

Answer 28

Blue solution to yellow solution

Question 29

What is the reagent, observation, and equation for the oxidation of Fe2+ to Fe3+?

Answer 29

Reagent: MnO4-
Observation: purple –> colourless
Equation: MnO4- + 8H+ + 5Fe2+ –> 5Fe3+ Mn2+ + 4H2O

Question 30

What is the reagent, observations, and equation for the reduction of Fe3+ to Fe2+?

Answer 30

Reagent: I-
Observations: 1. orange-brown –> pale green
2. colourless –> brown

Question 31

What is the reagent, observation, and equation for the reduction of Cr2O7(2-) to Cr3+?

Answer 31

Reagent: Zn
Observation: orange –> green
Equation: Cr2O7(2-) + 14H+ + 3Zn –> 2Cr3+ 7H2O + 3Zn2+

Question 32

What is the reagent, observation, and equation for the further reduction of Cr3+ to Cr2+?

Answer 32

Reagent: Excess Zn
Observation: green –> pale blue
Equation: Cr3+ + e- –> Cr2+

Question 33

What is the reagent, observation, and equation for the reduction of Cu2+?

Answer 33

Reagent: I-
Observation: blue –> brown solution + white ppt.
Equation: 2Cu2+ + 4I- –> 2CuI + I2

Question 34

What is the reagent, observation, and equation for the disproportionation of Cu(I) ions?

Answer 34

Reagent: Hot H2SO4
Observation: ? –> brown solid + blue solution
Equation: Cu2O + H2SO4 –> Cu + CuSO4 + H2O

Question 35

What is the reagent, observation, and equation for the oxidation of Cr3+ to CrO4(2-)?

Answer 35

Reagent: H2O2
Observation: green –> yellow
Equation: 3H2O2 + 2Cr(3+) + 10OH- –> 2CrO4(2-) + 8H2O