Developing metals Flashcards
Fill in the gaps
A loss of electrons is _____
A gain of electrons is ______
A reducing agent _____ some of its electrons to ____ something and gets _____ itself
The more powerful a reducing agent is the more easilly it cann be _____ itself
The oxidising agent ____ electrons saway from something to _____ and gets _____ itself
The more powerful an oxidising agent is the more easily it can be _____
Oxidation
Reduction
Donates
Reduce
Oxidised
Oxidised
Takes
Oxidise
Reduced
Reduced
What do you do to ionic half equations to combine and balance them?
Multiply up an cancel out the electrons
If the oxidising agent contains oxygen add H+ and H2O
What are the steps for a redox titration?
1) Measure out your reducing agent (Fe2+) using a volumetric pipette and put in a conical flask
2) Add dilute sulfuric acid in excess (H+ allows the oxidising agent to be reduced)
3) Add the oxidising agent (MnO4-) to the reducing agent using a burette
4) Stop at the first permanent pink colour
Describe the colour change in the redox titration
Manganate ions in potassium manganate are purple
When added to the reducing agent they are reduced to Mn2+ which are colourless
The reaction continues until all the reducing agent has reacted and the one drop too much will turn it pink
Describe and draw an electrochemical cell
Two different metals dipped in salt solutions of their own ions and connected by a wire and a KNO3 salt bridge
Electrons flow from the most reactive metal to the least
Does oxidation/ reduction happen at the anode or cathode?
Oxidation - anode
Reduction - cathode
What is the purpose of the salt bridge?
Complete the cell and balance out charged
Prevents charge from building up
What is the defenition of a transition metal?
forms at least one stable ion with an incompletely filled d orbital
What is the general configuration of a TM?
[Ar] 4sx 3dy
(4s fills and empties before 3d)
What are the TM exceptions and why?
Sc only makes Sc3+ which is a completley empty d orbital
Zn only makes Zn2+ which is a completley filled d orbital
What is the electron config of Cr and Cu and why?
Cr
[Ar] 4s1 3d5
- the 4s electron moves to 3d giving only unpaired electrons so there is less repulsion meaning its more stable
Cu
[Ar] 4s1 3d10
- the 4s electron moves to the 3d making a completely filled subshell which is more stable
What are the 4 characteristic chemical properties of TM?
- Act as catalysts
- Variable oxidation states
- Form coloured compounds
- Form complexes
Why are TM good homogeneous catalysts?
they have variable oxidation states so they accept and loose electrons easilly so can form intermediates
Why are TM good heterogeneous catalysts?
they use 4s and 3d for adsorption
Why do TM have variable oxidation states?
the 4s and 3d subshell have similar energies so there are no big jumps in sucsessive ionisation energy
What is a complex?
a central transition metal ions surrounded by ligands
What is a ligand?
species which donates a pair of electrons to a TM ion to forma dative bond
What describes a ligand which makes one, two or multiple dative bonds and give examples?
One - monodentate (water, ammonia, chlordie, cyanide)
Two - bidentate (1,2 - diamino ethane and ethanedioate)
Many - polydnetate/ hexadentate (6) (edta4-)
How are complexes written?
[TM ion (ligand 1) x (ligand 2) x] overall charge
x = coordination number
Name the shape and bond angle for the complexes if they have a coordination number of 2,4 or 6
2 - linear 180
4 - tetrahedral 109.5 or square planar 90 (rare)
6 - octahedral 90
What is a ligand substitution reaction and when do they occur?
When ligands are swapped for another
Happen if the new complex is more stable or if there is an increase in entropy
Why are complexed coloured?
When ligands surround a TM ions the 3d orbital splits in two sets creating an energy gap which corresponds to visible light this is absorbed to excite electrons from a low d orbital to a high one and the complimentary colour is transmitted
How can you change the colour of a complex?
change the…
TM ion
the oxidation state of the TM ion
the ligand
the coordiation number
What does a colorimeter do?
measures the absorbance of light
