Transition metals key memory

Question 1

What is an autocatalyst

Answer 1

A type of homogeneous catalyst where the product catalyses the reaction

Question 2

Give an example of autocatalysis

Answer 2

Mn2+ is a catalyst in the reaction between C2O42- and MnO4-
(Mn2+ is product & catalyst)

Question 3

State what the presence of an autocatalyst means about the rate of a reaction

Answer 3

As the reaction proceeds, amount of product increases and therefore the rate of reaction also increases due to more catalyst present

Question 4

What is the overall equation of the reaction between MnO4- and C2O42-

Answer 4

Question 5

Why is the initial reaction between MnO4- and C2O42- very slow

Answer 5

Reacting two negative ions together and so a high activation energy

Question 6

Write the two steps for the autocatalysis reaction between MnO4- and C2O42-

Answer 6

Question 7

Draw the structure of ethanedioate

Answer 7

Question 8

Draw the structure of
Ethane-1,2-diamine

Answer 8

Question 9

Draw the structure of cis-platin

Answer 9

Question 10

Draw the structure of tollens reagent

Answer 10

Question 11

What is the equation for calculating energy absorbed by electrons from the ground state to an excited state

Answer 11

∆E = hv = hc/λ

Question 12

State the 5 steps in measuring the concentration of transition metal ions in solution using colorimetry

Answer 12

1 - Set colourimeter to zero
2 - White light is filtered into a narrow range of frequencies producing monochromatic light
3- Monochromatic light passes through a sample held in a cuvette (some light is absorbed)
4 - Light which isn’t absorbed travels to the detector
5 - Draw a calibration graph by making up known concentration of metal solution and plot measured absorbance ( Then draw line of best fit)

Question 13

What is the chelate effect

Answer 13

A substitution of a monodentate ligand by a bi/multidentate ligand leading to an increase in entropy and therefore stability of a complex

Question 14

What 2 things are required to reduce VO₂⁺ to V²⁺

Answer 14

Zinc
Acidic solution

Question 15

Write the redox equation for the reduction of VO₂⁺ to VO²⁺

Answer 15

Question 16

Write the redox equation for the reduction of VO²⁺ to V³⁺

Answer 16

Question 17

Write the redox equation for the reduction of V³⁺ to V²⁺

Answer 17

Question 18

What is the general redox equation for when we add tollens reagent to an aldehyde

Answer 18

RCHO(aq) + 2(Ag(NH3)2)+(aq) + 3OH-(aq) –> RCOO-(aq) + 2Ag(s) + 4NH3(aq) + 2H2O(l)

Question 19

What can we do to find the concentration of a reducing agent (Fe2+/C2O42-)

Answer 19

Titrate against an oxidising agent (MnO4-)

Question 20

What are the 5 steps in finding the concentration of (Fe2+/C2O42-) in a redox titration - state colour changes for each

Answer 20

1- Place reducing agent (Fe2+/C2O42-) in a conical flask (unknown conc & vol) and add excess H2SO4
2- Place oxidising agent MnO4- in burette (known conc)
3 - Add MnO4- to conical flask until faint colour of MnO4- disappears (drop by drop near end point) - Purple to colourless for Fe2+/Colourless to light pink for C2O42-)
4- Read from bottom of meniscus at eye level how much MnO4- is added
5 - Record results to 2 D.P & repeat until you get 2 concordant results

Question 21

Why do we add excess H2SO4 to the reducing agent in a redox titration

Answer 21

Ensures the presence of sufficient H+ ions to allow reduction of oxidising agent

Question 22

What is the contact process

Answer 22

The use of vanadium to make H2SO4

Question 23

State the species and type of catalyst used in the contact process

Answer 23

V2O5
Homogeneous

Question 24

What reaction does V2O5 catalyse in the contact process

Answer 24

SO2 to SO3

Question 25

Write the 3 steps in the contact process with equations, and stating which species is oxidised/reduced in each step

Answer 25

Question 26

Sketch the energy profile for a homogeneous catalyst

Answer 26

Question 27

What is the overall equation for the oxidation of iodide ions using S2O82-

Answer 27

S2O82-(aq) + 2I-(aq) —-> I2(aq) + 2SO42-(aq)

Question 28

Why is the uncatalysed reaction of the oxidation of iodide ions using S2O82- very slow

Answer 28

Reacting two negatively charged ions and so they repel, meaning a high activation energy

Question 29

What catalyst is used in the oxidation of iodide ions using S2O82-. State what type of catalyst this is

Answer 29

Fe2+(aq)
Homogeneous catalyst

Question 30

Write the two equations displaying the use of an Fe2+ catalyst in the oxidation of iodide ions using S2O82-. State the intermediate formed

Answer 30

(1) S2O82-(aq) + 2Fe2+(aq) —-> 2Fe3+(aq) + 2SO42-(aq)
Fe3+ is intermediate which reacts with I- to produce I2:
(2) 2I-(aq) + 2Fe3+(aq) —> 2Fe2+(aq) + I2(aq)
Catalyst reformed

(Combine both equations to get overall equation)

Question 31

Draw the routes for Fe

Answer 31

Question 32

Draw the routes for Cu

Answer 32

Question 33

Draw the routes for aluminium

Answer 33

Question 34

What is the formula for the dichromate ion

Answer 34

Cr2O72-