Tranition metals

Question 1

What are transition metals

Answer 1

D block elements that have an ion with an incomplete d subshell.

Question 2

Electron configuration of chromium

Answer 2

3d5 4s1

Question 3

Electron configuration of copper

Answer 3

3d10 4s1

Question 4

Transition elements form compounds in which they have different oxidation states

Answer 4

For example Iron forms two different chlorides, Iron (2) chloride Fe2Cl and Iron (3) chloride Fe3Cl.

Question 5

Transition elements form coloured compounds

Answer 5

Potassium dichromate is bright orange and Nickel (2) sulfate is green.

Question 6

Transition elements and their compounds can act as a catalyst

Answer 6

Iron is used in the haber process to make ammonia from nitrogen and hydrogen. Nickel is used as a catalyst in the hydrogenation of alkenes, for example making margarine.

Question 7

A ligand

Answer 7

A molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond (dative covalent bond)

Question 8

A dative covalent bond or coordinate bond

Answer 8

A special kind of covalent bond, formed when one of the bonded atoms provides both of the electrons in a shared pair

Question 9

Coordinate number

Answer 9

Indicates the number of coordinate bonds attached to the central metal ion

Question 10

Example of a complex ion

Answer 10

[Cr(H2O)6] 2+

Question 11

Monodentate ligand

Answer 11

Only donates one pair of electrons

Question 12

Bidante ligand

Answer 12

Donates two pairs of elecrons to the central metal ion.

Question 13

Octohedral complex ion

Answer 13

Has a coordinate number of 6, bond angle of ninety degrees

Question 14

Tetrahedral complex ion

Answer 14

Most common shape for a complex ion with a coordinate number of four, bond angle is 109.5

Question 15

Square planar complex ion

Answer 15

Bond angle of ninety degrees, occurs with 8d elements ie platinum, gold and palladium

Question 16

Optical isomerism in octahedral complexes

Answer 16

Optical isomerism only occurs in octahedral complexes containing two or more bidente ligands. They are mirror images of each other, like a left and right hand

Question 17

Cis-platin drug

Answer 17

This is an anti-cancer drug which works by forming a platinum complex and binding to DNA and preventing it from replication. Activation of a cells own repair mechanism eventually leading to the death of the cancer containing cell.

Question 18

Cis isomerism square planar

Answer 18

Where the two identical groups are adjacent to each other, they are at ninety degrees to each other

Question 19

Trans isomerism square planar

Answer 19

When the two identical groups are opposite each other and are at 180 degrees to each other

Question 20

Monodentate ligands in octahedral complexes cis-trans

Answer 20

The cis isomerism has two identical groups adjacent to each other, they are at ninety degrees to each other. In the trans isomerism they are opposite each other and are 180 degrees apart.

Question 21

Bidentate ligand in octahedral complexes cis-trans

Answer 21

In cis they are adjacent, in trans they are opposite

Question 22

Ligand substitution

Answer 22

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

Question 23

Reaction of copper sulphate with ammonia

Answer 23

A pale blue precipitate of Cu(OH)2 is formed when only a couple of drops of ammonia is added. This precipitate then dissolves in excess ammonia to form a dark blue soloution

Question 24

Equation of copper hydroxide and ammonia

Answer 24

[Cu(H2O)6]2+(aq) + 4NH3(aq) —> [Cu(NH3)4(H2O)2]+2(aq) + 4H2O(l)
In this reaction 4 ammonia ligands have replaced 4 water ligands

Question 25

Reaction of copper with concentrated hydrochloric acid

Answer 25

A pale blue soloution changes colour to form a yellow soloution.

Question 26

Equation of copper with HCl

Answer 26

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

Question 27

Haemoglobin and oxygen

Answer 27

Haemoglobin is composed of four polypeptide chains. Each chain contains haem which has Fe2+ at its centre, oxygen can bing to haem and transport it round the body where it can be released, from the lungs. The haemoglobin can then carry CO2 back to the lungs.

Question 28

Haemoglobin and Carbon monoxide

Answer 28

CO binds more strongly to haemoglobin then O2. Leaving fewer haemoglobin molecules to bind to oxygen. Tissues can be starved of oxygen because less oxygen is carried round the body. This is an example of ligand substitution as CO molecules can replace oxygen molecules in haemoglobin. This reaction is not reversible and can lead to death

Question 29

Precipitation reaction

Answer 29

A reaction in which soluble ions, in separate solutions, are mixed together to produce an insoluble compound which forms a solid

Question 30

Precipitation reaction between Cu2+ and NaOH

Answer 30

Blue precipitate forms which is insoluble in excess NaOH Cu2+(Aq) + 2OH-(aq) —> Cu(OH)2 [Cu(H2O)2+(aq) + 2OH-(aq) —> [Cu(OH)2(H2O)4](s) +2H2O

Question 31

Precipitation reaction of Cu2+ with ammonia

Answer 31

A blue precipitate forms which re-dissolves to form a blue soloution [Cu(H2O)6]2+(aq) + 2NH3(aq) —> [Cu(OH)2(H2O)4](s) + 2NH4+(aq)

Question 32

Precipitation reaction of Fe2+ and NaOH

Answer 32

Pale green soloution reacts to form a green precipitate of Iron(2) hydroxide. Insoluble in excess NaOH but turns brown on the surface as Iron(2) is oxidised to Iron(3) Fe2+(aq) + 20H-(aq) -->Fe(OH)2(s) in air Fe(OH)2(s) -->Fe(OH)3(s)

Question 33

Precipitation reaction of Fe2+ with ammonia

Answer 33

Reacts in the same way as with aqueous NaOH forming Fe(OH)2(s)

Question 34

Precipitation reaction of Fe3+ and NaOH

Answer 34

Pale yellow soloution reacts to form an orange-brown precipitate of Iron(3) hydroxide, the precipitate is insolouble in excess NaOH Fe3+(aq) + 3OH-(aq) -->Fe(OH)3(s)

Question 35

Precipitation reaction of Fe3+ and NaOH

Answer 35

Reacts in the same way as with aqueous NaOH forming Fe(OH)3(s)

Question 36

Precipitation reaction of Mn2+ and NaOH

Answer 36

Pale pink soloution reacts to form a light brown precipitate of manganese(2) hydroxide which darkens on standing in air. The precipitate is insolouble in excess NaOH Mn2+(aq) + 2OH-(aq) -->Mn(OH)2(s)

Question 37

Precipitation reaction of Mn2+ with ammonia

Answer 37

Reacts in the same way as with aqueous NaOH forming Mn(OH)2(s)

Question 38

Precipitation reaction of Cr3+ with NaOH

Answer 38

Violet soloution reacts to form a grey-green precipitate of chromium(3) hydroxide. The precipitate is solouble in excess NaOH forming a dark green soloution Cr3+(aq) + 3OH-(aq) --> Cr(OH)3(s) Cr(OH)3(s) + 3OH-(aq) --> [Cr(OH)6]3-(aq)

Question 39

Precipitation reaction of Cr3+ with ammonia

Answer 39

Cr(OH)3 is a green precipitate which dissolves in excess ammonia to form [Cr(NH3)6]3+(aq) which is a purple soloution