Transition elements

Question 1

Define a transition element

Answer 1

A d-block element which forms at least one ion with a partially filled d sub-shell

Question 2

What are the 2 elements that are not considered transition elements and why?

Answer 2

Scandium and zinc- they do not form ions with partially filled d sub-shells, however they are still d block elements as the last electron goes into a d sub-shell

Question 3

What are 3 properties of transition elements?

Answer 3

-They can act as industrial catalysts (e.g. iron in the Haber process to make ammonia)
-They form coloured compounds
-They form compounds with different oxidation states

Question 4

What is the noble gas configuration of chromium?

Answer 4

[Ar]4s13d5

Question 5

What is the noble gas configuration of copper?

Answer 5

[Ar]4s13d10

Question 6

Which electrons do transition elements lose first when forming ions?

Answer 6

4s

Question 7

Define ligand

Answer 7

A species with a lone pair of electrons which it can donate to a metal ion to form a co-ordinate bond in a complex ion

Question 8

Define complex ion

Answer 8

A central metal ion surrounded by ligands which have formed co-ordinate bonds to the metal

Question 9

Define co-ordination number

Answer 9

The number of co-ordinate bonds formed by ligands to the central metal ion

Question 10

Define bidentate ligand

Answer 10

A ligand which donates 2 pairs of electrons to a metal ion, forming 2 co-ordinate bonds

Question 11

What shape is formed when there are 4 large ligands (e.g. chloride ions) around a central metal ion? What is the bond angle?

Answer 11

Tetrahedral, 109.5 degrees (or sometimes square planar, 90 degrees)

Question 12

What shape is formed when there are 6 small ligands (e.g. water or ammonia) around a central metal ion? What is the bond angle?

Answer 12

Octahedral, 90 degrees

Question 13

What is cis-platin?

Answer 13

This is an anti-cancer drug, existing as 2 stereoisomers cis and trans, in a square planar arrangement. It prevents DNA replication in cancer cells by a ligand replacement reaction with DNA. Effective for treating cancer, however is still toxic to healthy cells. Transplatin however is toxic.

Question 14

Transition metal ions + alkali —-> ?

Answer 14

Metal hydroxide (as precipitate)

Question 15

What does a reducing agent do?

Answer 15

Reduces other species but is oxidised itself

Question 16

What does an oxidising agent do?

Answer 16

Oxidises other species but is reduced itself

Question 17

What are the steps you should follow to write half equations?

Answer 17

1) Oxidation or reduction?
2) How many electrons lost or gained?
3) Put electrons on correct side
4) Balance O using H2O
5) Balance H2O with H+
6) Balance charges and atoms

Question 18

What is the ratio for MnO4- and Fe2+

Answer 18

1:5

Question 19

Why can HCL not be used for a potassium manganate titration?

Answer 19

It would oxidise Cl- to Cl2, so would affect the volume of KMnO4 required

Question 20

Why can ethanoic acid not be used in a potassium manganate titration?

Answer 20

It is a weak acid so wouldn’t provide enough H+ ions

Question 21

Why can concentrated H2SO4 or HNO3 not be used in a potassium manganate titration?

Answer 21

They are oxidising agents themselves so affect volume of KMnO4 required

Question 22

What acid is used in excess in the potassium manganate titration and why?

Answer 22

Dilute H2SO4 to prevent the reducing agent from oxidising

Question 23

What is the ratio for MnO4- and C2O4-

Answer 23

2:5

Question 24

What colour does the solution go in a iodine-thiosulfate titration?

Answer 24

Brown, then the precipitate is off-white. Once starch is added, it turns deep blue. The end point is when this fades.

Question 25

What colour is the end point in the potassium manganate titration?

Answer 25

Pale pink

Question 26

What is the ratio for Cu2+ and sodium thiosulfate?

Answer 26

2:2 (divide by 2 to find I- moles)