F325 - Transition Elements

Question 0

What metals are not transition elements and why?

Answer 0

Scandium and zinc.
They do not have any ions with partially filled d orbitals.

Sc3+ has an empty d orbital.
Zn2+ has a completely full d orbital.

Question 1

What is a transition element?

Answer 1

A d block element that forms an ion with an incomplete d sub shell.

Question 2

What sub shells overlap?

Answer 2

4s before 3d.

Also lost before.

Question 3

What metals do not fill regularly?

Answer 3

Chromium: the 3d and 4s all contain 1 electron with no completely filled.

Copper contains full 3d orbitals but only 1 electron in the 4s orbital.

Question 4

Describe how metals act as effective catalysts.

Answer 4

Provide a surface on which the reaction can take place.
Reactants are adsorbed onto the surface of the metal and held in place while the reaction occurs.
The products are then designed and the metal is unchanged.

Can change oxidation states by losing or gaining electrons, they can bind to reactants forming intermediates as part if a chemical pathway with a lower activation energy.

Question 5

Describe the Haber process.

Answer 5

N2 + 3H2 —> 2NH3 all (g)

Makes ammonia.
Iron catalyst increases rate and lowers temp for reaction.

Ammonia used in manufacturing fertilisers.

Question 6

Describe the contact process.

Answer 6

Sulphur dioxide -> sulphur trioxide in the manufacturing of sulphuric acid (H2SO4).

2SO2 + O2 —> 2SO3

Vanadium (V) oxide. V2O5

Production of fertilisers.

Question 7

Describe the hydrogenation if alkenes.

Answer 7

C2H4 + H2 —> C2H6

Nickel catalyst lowers temp and pressure.

Hydrogenation if unsaturated veg oils.

Question 8

Describe the decomposition of hydrogen peroxide.

Answer 8

2H2O2 (aq) —> 2H2O + O2

Manganese (IV) oxide. MnO2.

Preparation of oxygen gas.

Question 9

Describe the reaction of metals with NaOH

Cu2+
Co2+
Fe2+
Fe3+

Answer 9

Cu2+ : pale blue solution -> pale blue precipitate.

Co2+ : pink solution -> blue precipitate. Beige in air.

Fe2+ : pale green -> green precipitate. Turns rusty brown at surface standing in air.

Fe3+ : pale yellow -> rusty brown.

Metal2+ + 2OH —> metal(OH)2
3 3 OH3

Question 10

What is a complex ion?

Answer 10

A transition metal bonded to one or more Ligands by co ordinate bonds (dative covalent bond)

Question 11

What is a ligand?

Answer 11

A molecule or ion that can donate a pair of electrons with the transition metal ion to form a co ordinate bond.

Question 12

What is a co ordinate bond?

Answer 12

A bond in which one of the bonded atoms provides both electrons for the shared pair.
Dative for transition metals.

Question 13

What Is a monodentate ligand?

Answer 13

The Logan donates only one pair of electrons to the central metal ion to form one co ordinate bond.

Question 14

What is the most common shape of complex ions?

Answer 14

Octahedral with 6 co ordinate bonds.

All bond angles are 90 degrees.

Question 15

What are stereoisomers?

Answer 15

Species with the same structural formula but with a different arrangement if the atoms in space.

Question 16

what is cis/trans isomerism?

Answer 16

Cis: the two Cl- Ligands are adjacent on a corner, at 90 degrees from each other.

Trans: two Cl- Ligands are opposite, at 180 degrees from each other.

Question 17

What is a bidentate ligand?

Answer 17

It can donate two lone pairs to the central metal ion to form two co ordinate bonds.

Question 18

What is optical isomerism?

Answer 18

Non superimposable mirror images.

Mirror image flip.

Question 19

What is ligand substitution?

Answer 19

A reaction in which one ligand in a complex ion is replaced by another ligand.

Question 20

Describe the reaction of aqueous copper ions and ammonia.

Answer 20

Pale blue aqueous copper ions.
When excess aqueous ammonia is adde it forms a deep blue solution.

4 of the water Ligands are replaced by four ammonia Ligands.

[Cu(H2O)6]2+ + 4NH3 ><
[Cu(NH3)4(H2O)2]2+ + 4H2O

If only a small amount of ammonia is added Cu(OH)2 forms, which forms a pale blue precipitate.

Question 21

Describe the reaction of copper (II) ions and hydrochloric acid.

Answer 21

The aqueous solution containing copper (II) ions is a pale blue solution, when HCL is added it turns to a green solution, then to yellow.

[Cu(H2O)6]2+ + 4Cl- <>
[CuCl4]2- + 6H2O

Chlorine Ligands are larger than water Ligands and have stronger repulsions. This forms a tetrahedral shape with 4 Ligands.

Question 22

Describe the reaction of cobalt (II) ions and conc hydrochloric acid.

Answer 22

An aqueous solution of colbalt (II) ions has a pale pink colour. When conc HCL is added the solution changes to dark blue.

[Co(H2O)6]2+ + 4Cl- ><
[CoCl4]2- + 6H2O

The six water molecules in the complex ion are replaced by four chlorine ions.

Question 23

Why is carbon monoxide and haemoglobin an example of ligand substitution?

Describe haemoglobin.

Answer 23

Carbon monoxide binds more strongly to haemoglobin than oxygen. If both are present CO will bind and replace if O2 is already present.
Irreversible.

Fe2+ haem group forms a co ordinate bond to oxygen.

Question 24

What is the stability constant?

Kstab

Answer 24

The equilibrium constant for an equilibrium existing between a transition metal ion surrounded by water Ligands and the complex formed when the same ion has undergone a ligand substitution.

Question 25

Why Is H2O ignored when calculating Kstab?

Answer 25

All the species are dissolved in water Which is in large excess.
It’s concentration is virtually constant.

Question 26

What does a high Kstab indicate?

Answer 26

It is more stable than those with lower constants.

The position of eq lies to the right.

Question 27

What is the equation for MnO4- + Fe2+?

Answer 27

MnO4- + 8H+ + Fe2+ —> Mn2+ + 5Fe3+ + 4H2O.

Fe2+ —> Fe3+ + e-

MnO4- + 8H+ + 5e- —> Mn2+ + 4H2O

Question 28

What is the equation for iodine and thiosulphate?

Answer 28

2S2O3 2- + I2 —> 2I- + S4O6 2-