Transition metals

Question 1

Transition metal row and how the characteristics arise

Answer 1

Sc->Cu

arise from an incomplete d sublevel in atoms or ions

Question 2

4 transition metal characteristics

Answer 2

complex formation
formation of coloured ions
variable oxidation states
catalytic activity

Question 3

Why is zinc not a transition metal

Answer 3

only forms 2+ ions
has a complete d orbital as a 2+ ion
does not meet “incomplete d orbital in a compound” criteria

Question 4

complex definition

Answer 4

central metal ion surrounded by ligands

Question 5

ligand definition

Answer 5

atom/ion/molecule that can donate a lone electron pair

Question 6

coordinate bond definition

Answer 6

shared pair of electrons in the covalent bond come from one of the bonding atoms

Question 7

3 monodentate ligands

Answer 7

H2O
NH3
Cl-

Question 8

2 bidentate ligands

Answer 8

1,2-diaminoethane
ethanedioate ion (C2O42-)

Question 9

multidentate ligand

Answer 9

EDTA4-

Question 10

which monodentate ligand can displace the other 2?

Answer 10

Cl- as it is larger

Question 11

chelate effect

Answer 11

monodentate ligand substituted by a bidentate/multidentate ligand for a more stable complex
due to positive entropy change as theres more moles of products than reactants

Question 12

Why is it useful that EDTA is stable?

Answer 12

add to rivers to remove heavy metal ions as EDTA complexes aren’t toxic

Question 13

What does a transition metal’s complex colour depend on?

Answer 13

coordination number of the complex
type of ligand bonded to the ion
oxidation state

Question 14

how is colour observed

Answer 14

the transition metal complex absorbs certain wavelengths, exciting electrons into a higher energy level and the remaining wavelengths are reflected and transmitted to the eye

Question 15

change in energy (plancks constant eqn) and what the letters mean + units

Answer 15

ΔE= hc/λ = hυ

h plancks constant 6.63x10-34
λ wavelength in m
υ frequency in Hz

Question 16

describe colorimetry

Answer 16

analytical technique
uses absorption of visible light
to determine conc of coloured ions
by measuring absorbance

Question 17

calibration graph axes

Answer 17

x = concentration
y = absorbance

Question 18

Oxidation states of vanadium, ion formulae of each and ion colours

Answer 18

5 VO2+ yellow
4 VO^2+ blue
3 V3+ green
2 V2+ violet

You Better Get Vanadium

Question 19

Reduction reaction of vanadium with zinc, requiring acidic conditions?

Answer 19

standard balanced acidic condition redox reaction with bigger oxidation number on left

Question 20

Tollens reagent test for aldehydes equation

Answer 20

RCHO + 2[Ag(NO3)2]+ + 2OH- ->
RCOO- + 2Ag + 4NH3 + 2H2O

Question 21

C2O4 2- redox titration products

Answer 21

2CO2 + 2e-

Question 22

heterogenous catalyst example

Answer 22

haber process solid iron catalyst for hydrogen and nitrogen gas reaction

Question 23

why do transition metals make good catalysts

Answer 23

variable oxidation states
electrons are transferred to produce a reactive intermediate
this speeds up reaction rate

Question 24

Heterogenous reaction overall equation and intermediate reactions

Answer 24

2SO2 + O2 -V2O5> 2SO3

2V2O5 + 2SO2 -> 2V2O4 + 2SO3
2V2O4 + O2 -> 2V2O5

Question 25

Catalyst adsorption

Answer 25

solid catalysts adsorb molecules onto an active site on the surface of the catalyst these active sites increase proximity of molecules + weaken covalent bonds + increasing rate of reaction

Question 26

what is catalyst poisoning?

Answer 26

impurities block active sites of heterogenous catalysts molecule's covalent bonds stay intact catalyst has no effect on ROR

Question 27

the problem with catalyst poisoning + an example of it

Answer 27

increased chemical production costs catalyst must be replaced/cleaned regularly sulfur impurities poison the solid iron catalyst in the Haber process

Question 28

Homogenous catalyst overall equation and intermediate reactions

Answer 28

S2O8 2- + 2I- -Fe2+> I2 + 2SO4 2- S2O8 2- + 2Fe2+ -> 2Fe3+ + 2SO4 2- 2Fe3+ + 2I- -> 2Fe2+ + I2

Question 29

Why is a Fe2+ catalyst needed for S2O82- and 2I- to react?

Answer 29

energy needed to overcome repulsive forces as they're both negatively charged

Question 30

autocatalysis reaction is

Answer 30

a redox reaction between MnO4- ions and C2O42-

Question 31

during colorimetry, what must be done before taking absorbance

Answer 31

add an appropriate ligand to intensify the colour