DM

Question 1

electronic configuration of chromium

Answer 1

lower energy given by putting one electron in each 3d and 4s orbital, rather than 2 electrons in 4s

Question 2

electronic configuration of copper

Answer 2

lower energy given by putting 2 electrons in each 3d orbital and one electron in 4s, rather than 9 electrons in 3d and 2 in 4s

Question 3

transition metals form ions by losing electrons first from

Answer 3

the 4s orbital

Question 4

transition metals forming ions

Answer 4

form one or more stable ion which have INCOMPLETELY FILLED D-ORBITALS

Question 5

zinc and scandium as transition metals

Answer 5

often not considered transition metals
zinc only forms Zn (II) which has full d-orbitals
scandium only forms Sc (III) which has empty d-orbitals

Question 6

potassium manganate (VII)

Answer 6

purple compound

can oxidise Fe (II) to Fe (III)

Question 7

catalyst

Answer 7

alters rate of chemical reaction but remains chemically unchaged in the process

Question 8

transition metals as catalysts

Answer 8

it is the availability of 3d and 4s electrons and the ability to change oxidation state that help make transition metals good catalysts

Question 9

heterogeneous catalysis

Answer 9

catalyst in different physical state to reactants

transition metals can used 3d and 4s electrons to form weak bonds to reactants (chemisorption)

Question 10

homogeneous catalysis

Answer 10

catalyst in same physical state as reactants

usually involves in transition metal ion forming an intermediate compound with one or more reactants

Question 11

reaction of Fe (II), Fe (III) and Cu (II) with ammonia solution and NaOH

Answer 11

form copper (II) hydroxide, iron (II) hydroxide and iron (III) hydroxide

if source of OH- is ammonia solution, the copper (II) hydroxide precipitate will redissolve on addition of excess ammonia solution to form a purple-blue solution

Question 12

effect of ligands on colour of compounds

Answer 12

there are 5 d orbitals in d-block metals

ligands cause these orbitals to split in such a way that some are slightly higher in energy level than other
the deltaE between the two levels is now such that the light absorbed falls in the visible part of the spectrum

transmitted light is the light that is not absorbed, and is the colour seen

Question 13

monodentate ligand

Answer 13

can only form one dative/coordinate bond to central metal ion (eg. halides, cyanide, hydroxide)

Question 14

ligands

Answer 14

negatively charged ions or neutral molecules possessing a lone pair of electrons
attach themselves to the central metal ion by using a lone pair of electrons to form a dative/coordinate bond
cause the five d orbitals to split into different energy levels

Question 15

effect of concentration of solution on the light it absorbs and the colour it appears

Answer 15

more concentrated solution, more light absorbed, darker colour of solution

Question 16

colorimetry

Answer 16

used to determine concentration of substance
narrow beam of white light passed through coloured filter
colour of filter must correspond to the colour of light most strongly absorbed (complimentary to colour of light emitted/seen)

Question 17

potential difference

Answer 17

a measure of how much each electrode is tending to accept/release electrons
measured in Volts
one volt = one joule of energy tranferred per coulumb of charge

Question 18

Ecell

Answer 18

the potential difference in an electrochemical cell when no current flows
difference in the elctrode potential of each half cell

Question 19

more positive electrode potential of half cell

Answer 19

greater tendency to accept electrons (be reduced)

Question 20

more negative electrode potential of half cell

Answer 20

lesser tendency to accept electrons

Question 21

purpose of salt bridge between half cells

Answer 21

carry current between half cells

complete circuit

Question 22

standard hydrogen half cell

Answer 22

used as a reference, all other half cells measured against it
standard conditions (1 moldm-3 solution of H+ , 298K, platinum electrode, hydrogen gas bubbled into solution)

Question 23

when no metal in half reaction, a electrode which is

Answer 23

unreactive is used (eg. platinum)

Question 24

rust

Answer 24

a hydrated form of iron III oxide > Fe2O3.xH2O

Question 25

process of rusting

Answer 25

when a water droplet is left in contact with iron/steel, the conc of dissolved oxygen in the water droplet determines which regions of the metal surface are sites of red or ox
at centre of droplet, oxygen conc is low so iron is oxidised
at edges of droplet, conc of dissolved O2 is higher, so oxygen is reduced to OH using electrons from oxidation of iron
Fe (II) and hydroxide react to form iron (II) hydroxide
iron (II) hydroxide is oxidised to hydrated iron (III) oxide

Question 26

rusting equations

Answer 26

Fe (s) Fe (II) (aq) + 2e- [NEGATIVE ELECTRODE]

1/2(O2) (g) + H2O (l) + 2e- 2OH- (aq) [POSITIVE ELECTRODE]

Question 27

sacrificial protection of iron

Answer 27

use metals with more negative electrode potential (eg. Zn or Cr)
sacrificial metal is oxidised so that iron is not, preventing formation of Fe (II)

Question 28

complex

Answer 28

central metal atom/ion surrounded by ligands

may have a +ve charge, -ve charge or no charge

Question 29

charged complex =

Answer 29

complex ion

Question 30

coordination number

Answer 30

number of bonds from the central ion to its ligands

Question 31

shapes relating to coordination number

Answer 31

6 - octahedral
4 - tetrahedral (sometimes square planar)
2 - linear

Question 32

ligand substitution reaction

Answer 32

ligands can displace other ligands
this occurs if the new complex formed is more stable than the previous complex
therefore, stability of complex is dependent on its ligands