Transition metals

Question 1

What is a transition metal?

Answer 1

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

Question 2

What are the two types of catalysts that transition metals can act as?

Answer 2

Transition metals can act as heterogenous catalysts.

Transition metals in solution can act as homogenous catalysts

Question 3

What are some examples of heterogenous transition metals catalysts?

Answer 3

1. Iron in Haber process, iron is solid while N2 and H2 are gases
2. Vanadium oxide in the contact process
3. Finely divided nickel in hydrogenation reactions
4. Platinum in the catalytic oxidation of ammonia

Question 4

How do heterogenous catalysts work?

Answer 4

Chemisorption.
Reactant molecules are absorbed onto the surface of the molecule,the bonds are weakened and the molecules are help in a more favourable orientation for the reaction

Question 5

What are some physical properties of transition metals?

Answer 5

1. Good conductor of electricity
2. Often coloured in aqueous solution
3. Many form coloured complexes
4. The aqueous metal ions are actually hexaaqua cations

Question 6

What is a complex?

Answer 6

A central metal atom or ion with ligands bonded by coordinate bonds.

Question 7

What is a ligand?

Answer 7

An ion or molecule with a lone pair of electrons which forms a coordinate bond with a central metal atom or ion in a complex

Question 8

How are complexes often written?

Answer 8

on page

Question 9

What are three neutral ligands?

Answer 9

Aqua - H2O
Ammine - NH3
1,2-diaminoethane (en) -H2NCH2CH2NH2

Question 10

What are four anion ligands?

Answer 10

Chloro - Cl-
Cyano - CN-
Thiocyano - SCN-
Edta4-

Question 11

What is a monodentate ligand?

Answer 11

A ligand which uses only one lone pair of electrons to form a coordinate bond with a central metal atom or ion in a complex

Question 12

What is a bidentate ligand?

Answer 12

A ligand which uses two lone pairs of eletrons to form two coordinate bonds with a central metal atom or ion in a complex

Question 13

What is a polydentate ligand?

Answer 13

A ligand which uses many lone pairs of electrons to form more than two coordinate bonds with a central metal atom or ion

Question 14

If a ligand is neutral then what do you do?

Answer 14

If a ligand is neutral, then the charge on the complex is the same as that of the metal ion

Question 15

What do you do if the ligand is negatively charged

Answer 15

If the ligand is negatively charged then the charge on the ligand is the number on the metal ion + (number of ligands x negative charge)

Question 16

Why is H2O monodentate?

Answer 16

H2O is monodentate because although it has two lone pairs they cannot separate enough to form separate coordinate bonds

Question 17

Draw the order of the strength of ligands

Answer 17

The strength depends on the availability of the lone pair of electrons ease of donation
CN-, en, NH3, H2O, OH-, F-, Cl-, Br-, I-
→ decreasing ligand strength

Question 18

Why does the strenght of the ligand decrease down the halides

Answer 18

The bond is longer therefore weaker

Question 19

What do alkyl groups do?

Answer 19

They push electrons towards the N atom, destabilising the lone pair, so it is more likely to be donated to the central metal atom or ion in the complex

Question 20

What is ligand replacement?

Answer 20

A stronger ligand can replace a weaker ligand in a complex

Question 21

table of chronium

Answer 21

on page

Question 22

How do you reduce vanadium?

Answer 22

Use zinc in the presence of dilute hydrochloric acid.

Question 23

How is the +5 oxidation state of zinc achieved

Answer 23

Using an acidified solution of ammonium vanadate (V), NH4VO3. VO3- ionds where V is +5

Question 24

Write the equations for the reduction of vanadium

Answer 24

on page

Question 25

How are complexes named?

Answer 25

Based on the number and name of ligands and the mteal ion with the oxidation state e.g.
[Fe(H2O)6]3+ = hexaaquairon (III)