Transition metals key memory Flashcards
Autocatalysis, Contact process, Homogeneous catalyst, Vanadium reduction, Redox titration
What is an autocatalyst
A type of homogeneous catalyst where the product catalyses the reaction
Give an example of autocatalysis
Mn2+ is a catalyst in the reaction between C2O42- and MnO4-
(Mn2+ is product & catalyst)
State what the presence of an autocatalyst means about the rate of a reaction
As the reaction proceeds, amount of product increases and therefore the rate of reaction also increases due to more catalyst present
What is the overall equation of the reaction between MnO4- and C2O42-
Why is the initial reaction between MnO4- and C2O42- very slow
Reacting two negative ions together and so a high activation energy
Write the two steps for the autocatalysis reaction between MnO4- and C2O42-
Draw the structure of ethanedioate
Draw the structure of
Ethane-1,2-diamine
Draw the structure of cis-platin
Draw the structure of tollens reagent
What is the equation for calculating energy absorbed by electrons from the ground state to an excited state
∆E = hv = hc/λ
State the 5 steps in measuring the concentration of transition metal ions in solution using colorimetry
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)
What is the chelate effect
A substitution of a monodentate ligand by a bi/multidentate ligand leading to an increase in entropy and therefore stability of a complex
What 2 things are required to reduce VO₂⁺ to V²⁺
Zinc
Acidic solution
Write the redox equation for the reduction of VO₂⁺ to VO²⁺
Write the redox equation for the reduction of VO²⁺ to V³⁺
Write the redox equation for the reduction of V³⁺ to V²⁺
What is the general redox equation for when we add tollens reagent to an aldehyde in basic conditions
RCHO(aq) + 2(Ag(NH3)2)+(aq) + 3OH-(aq) –> RCOO-(aq) + 2Ag(s) + 4NH3(aq) + 2H2O(l)
What can we do to find the concentration of a reducing agent (Fe2+/C2O42-)
Titrate against an oxidising agent (MnO4-)
What are the 5 steps in finding the concentration of (Fe2+/C2O42-) in a redox titration - state colour changes for each
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
Why do we add excess H2SO4 to the reducing agent in a redox titration
Ensures the presence of sufficient H+ ions to allow reduction of oxidising agent
What is the contact process
The use of vanadium to make H2SO4
State the species and type of catalyst used in the contact process
V2O5
Homogeneous
What reaction does V2O5 catalyse in the contact process
SO2 to SO3
Write the 3 steps in the contact process with equations, and stating which species is oxidised/reduced in each step
Sketch the energy profile for a homogeneous catalyst
What is the overall equation for the oxidation of iodide ions using S2O82-
S2O82-(aq) + 2I-(aq) —-> I2(aq) + 2SO42-(aq)
Why is the uncatalysed reaction of the oxidation of iodide ions using S2O82- very slow
Reacting two negatively charged ions and so they repel, meaning a high activation energy
What catalyst is used in the oxidation of iodide ions using S2O82-. State what type of catalyst this is
Fe2+(aq)
Homogeneous catalyst
Write the two equations displaying the use of an Fe2+ catalyst in the oxidation of iodide ions using S2O82-. State the intermediate formed
(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)
Draw the routes for Fe
Draw the routes for Cu
Draw the routes for aluminium
What is the formula for the dichromate ion
Cr2O72-
