Developing Metals Flashcards
a transition metal is…
a d-block element that can form at least one stable ion with an incomplete sub shell
variable oxidation state means…
an element that can have multiple oxidation states
what oxidation states can iron exist as?
Fe 2+ and Fe3+
what oxidation states can copper exist as?
Cu+ and Cu2+
transition metals form _____ ions in solution
coloured
Fe 2+ ions in solution are…
pale green
Fe 3+ ions in solution are…
yellow
Cu2+ ions in solution are…
blue
metals have giant _____ _____structures
metallic lattice
how are metallic bonds created?
the electrons in the outer shell are delocalised and free to move, leaving a positive metal ion. this ion is attracted to delocalised electrons and form a sea of closely packed positive ions in a sea of delocalised electrons
explain the order of filling of the 3d and 4s sub shell in terms of every level and spin pairing
The electrons fill up sub shells from the lowest energy level first. The 4S sub shell has a lower energy level than the 3D sub shell, which means it fills up first
write the electron configuration for Fe2+
1s2 2s2 2p6 3s2 3p6 3d6
write the electron configuration for Cu2+
1s2 2s2 2p6 3s2 3p6 3d9
copper prefers to have a ___ 3d sub shell and just ___ electron in the ___ sub shell
full
one
4s
write a method to determine the concentration of Fe2+ ions in a solution of iron chloride by titration
- put 25cm3 of iron chloride in conical flasks using pipette
- fill burette with standard solution of KMnO4
- add KMnO4 until permanent colour change to pink
- Record volume added
- Repeat for concordant results
why is zinc not classified as a transition metal?
there are no zinc ions with an incomplete sub shell
what properties does a transition metal have?
•the existence of more than one oxidation state in its compounds
•the formation of coloured ions
a heterogenous catalyst is…
A catalyst that is in a different state to the reactants
a homogenous catalyst is…
A catalyst that is in the same state as the reactants
why are transition metals good catalysts?
they have multiple oxidation states so can easily gain an electron and then give it back or can easily lose an electron and gain it back
a ligand is…
a molecule or ion with an available lone pair of electrons to form a covalent bond
a complex ion is…
a transition metal ion surrounded by one or more ligands
a d-orbital is…
a space where you could find a pair of electrons in a D sub shell
Explain why transition metals in solution are coloured
ligands split the d-orbitals into slightly different energy levels, creating a small gap between energy levels. E=hv so this gap creates a wavelength in the visible range. visible frequencies absorbed and complimentary colours are transmitted
why are transition metal ions coloured when hydrated?
water off crystallisation acts as ligand causing d orbitals to split and cause a gap in energy levels in the visible range so complementary colour transmitted
why are transition metal ions not coloured when anhydrous?
anhydrous don’t have ligands so energy gap between levels is too large and out of the viable range so no cloud seen
explain why group 1 and 2 metals are not coloured
don’t have partially filled d sub shells so electrons can’t be promoted from one d orbital to another causing a split. Therefore the energy gap is too large and out of the visible range so not coloured
give the ionic equation for when Fe2+ reacts with NaOH solution
Fe2+ + 2OH- —> Fe(OH)2
what is observed when Fe2+ ions react with NaOH
green gelatinous precipitate
give the ionic equation for when Fe3+ reacts with NaOH solution
Fe3+ + 3OH- —> Fe (OH)3
what is observed when Fe3+ ions react with NaOH
orange/brown gelatinous precipitate
give the ionic equation for when Cu2+ reacts with NaOH solution
Cu2+ + 2OH- —> Cu (OH)2
what is observed when Cu2+ ions react with NaOH
blue gelatinous precipitate
what is observed when Fe2+ ions react with ammonia solution
green gelatinous precipitate
give the ionic equation for Fe2+ ions and ammonia solution and explain why
Fe2+ + 2OH- —> Fe (OH)2
the Fe 2+ doesn’t form a complex with NH3. NH3 is an alkali.
give the ionic equation for Fe3+ ions and ammonia solution and explain why
Fe3+ + 3Oh- —> Fe (OH)3
the Fe 3+ doesn’t form a complex with NH3. NH3 is an alkali.
what is observed when Fe3+ ions react with ammonia solution
orange/brown gelatinous precipitate
what is observed when Cu2+ ions react with a few drops of ammonia solution
blue precipitate
give the ionic equation for Cu2+ ions with a few drops of ammonia solution
2H2O + 2NH3 —> 2NH4+ + 2OH-
give the ionic equation for Cu2+ ions with excess of ammonia solution
[Cu(H2O)6]2+ + 6NH3 —> [Cu(H2O)4(OH)2] + 6H2O
what is observed when Cu2+ ions react with excess of ammonia solution
darker blue solution
describe how to set up an experiment to determine the concentration of a Cu2+ solution using colourimetry
1.choose a complimentary colour filter for the colourimeter
2.make a series of known concentrations of Cu2+ and test absorbance
3. use results to plot a calibration curve
4. test the absorbance of the unknown sample and use calibration curve to find its concentration
define standard electrode potential
the voltage measured under standard conditions when the half cell is connected to a standard hydrogen electrode
how do you calculate standard cell potential
more positive half cell voltage - more negative half cell voltage
what is the electrochemical series?
list of redox equilibrium arranged from most -ve electrode potential at the bottom and more +be at the bottom
what are standard conditions?
298k temp
100kPa pressure
solutions of 1.0 mol dm-3
what are the limitations of predicting the feasibility of redox reactions using standard electrode potential data?
- electrode potential values are at standard conditions but not all reactions occur at standard conditions
- doesn’t consider activation energy
what is a salt bridge made from?
filter paper soaked in KNO3
define corrosion
damage to the metal caused by its reaction with the environment
give the overall equation for the rusting of iron
2Fe + 3O2 + 2H2O —> Fe2O3•xH2O
explain how painting prevents rusting
the paint creates a barrier between the iron and the oxygen
explain how galvanising prevents rusting
coating of more reactive metal which reacts to form an oxide that seals the metal below from O2
explain how sacrificial protection prevents rusting
a more reactive metal is attached and oxides first protecting the other metal
explain how plating prevents rusting
coating the iron in an unreactive metal, sealing if from O2
explain how impressed current prevents rusting
forces the metal to become a positive electrode, the system goes forwards not allowing them to oxidise
in rusting,
give the half equation of the formation of Fe 2+ ions
and is this oxidation or reduction
Fe —> Fe2+ + 2e-
oxidation
in rusting,
give the half equation for the formation of OH- ions
and is this oxidation or reduction
O2 + 2H2O + 4e- —> 4OH-
reduction
give an ionic equation for the formation of green rust
Fe2+ + 2OH- —> Fe(OH)2
give the oxidation state of red/brown rust
+3
suggest why in some conditions green rust forms instead of red on steel underground pipes
low oxygen so Fe3+ isn’t oxidised further to Fe3+
a ligand is….
a molecule with a lone pair that is available to form a coordinate bond
a complex ion is…
metal surrounded by ligands that are co-ordinatley bonded by a ligand donating electron to the ion
a co-ordinate bond is…
a dative covalent bond between a ligand and a central metal ion
co-ordinate number is…
the number of coordinate bond in a complex ion
bidentate is…
two lone pairs of a ligand to form 2 coordinate bonds with a TM ion
multidentate
more than two lone pairs of ligand to form more than two coordinate bonds with TM ion
what does a species need to act as a ligand?
available lone pair of electrons
explain how a coordinate bond forms
a ligands forms a dative covalent bond with the central TM ion by donating both electrons in the shared pair
what shape molecule is copper hexa aqua?
octahedral
explain why [Cu (H2O)6]2+ has a charge of 2+
Cu2+ is the central metal ion
6 ligands all neutral
so overall charge 2+
how many co ordinate bonds does EDTA form?
6
how does EDTA form a polymer chain
it forms 6 co ordinate bonds. 3 form in each direction to the TM ion to form a polymer chain with repeating units
bidente ligands have a ______ shape with a bond angle of ____
octahedral
90 degrees
how would chemists dissolve a iron nail and make the solution up to 1 dm3?
dissolve the nail in warm sulfuric acid and transfer it to a 1dm3 volumetric flask and make it up to the mark
when a ligand substitution occurs why is there a colour change?
a new ligand splits p-orbitals differently
in a bidentate ligand the shape is… and bond angle is …..
octahedral
90 degrees
