Developing Metals Flashcards
Describe how you would do a manganate(Vii) titration?
Measure out a quantity of reducing agent-Fe2+ with a pippette and put in conical flask
Add sulfuric acid (in excess)
Add MnO4- using a burette and swirl flask
When turns pink all reducing agent has been used up
What shape are complexes with 4 coordinate bonds and what angles?
Square planar-90
Tetrahedral-109.5
Which electrode does oxidation occur?
Anode(positive)
Which electrode does reduction occur?
Cathode(negative)
In drawings of electrochemical cells which way round should the electrodes be?
Anode on the left and cathode on the right
How do you measure the Ecell?
More positive standard electrode potential- more negative standard electrode potential
How do you make a full reaction equation for a cell?
The more positive half equation goes forward and more negative goes back
Must equalise the electrons
Name 3 ways you can prevent rusting?
Painting with a polymer
Oiling/greasing
Sacrificial metal
State the 4 steps of rusting
Fe reacts with water and oxygen to make Fe2+ and OH-
Fe2+ + 2OH- ——-> Fe(OH)2
Reacts with water and oxygen
To make Fe(OH)3
Gradually turns into Fe2O3•H20
5 properties I’d transition metals
More than one stable ions
Ions have incomplete d orbitals
Formation of complexes
Formation of coloured ions
Ability to act as homogeneous or heterogeneous catalysts
What colour is Fe2+
Pale green
What colour is. Fe3+?
Yellow
What colour is Cu2+?
Blue
What colour is Cu+?
Colourless
Show Fe2+ in water complex
|Fe(H2O)6|2+
Show Fe3+ complex in water
|Fe(H2O)6|3+
Show Cu2+ complex in water
|Cu(H2O)6|2+
Show Cu2+ complex with ammonia
Cu(NH3)4 2+
Show complex of Cu2+ with chlorine
CuCl4 2-
What do you call a ligand with 2 lone pairs?
Bidentate
What is a coordinate bond?
Daitive covalent
What is ethandioate?
A bidentate Ligand
What colour is
|Cu(H2O)6|2+?
Blue solution
what colour is Cu(OH)2?
Pale blue precipitate
What colour is
|Cu(NH3)4|2+?
Deep blue
What colour is |CuCl4|2-?
Yellow
What colour is
|Fe(H2O)6|2+?
Green solution
What colour is Fe(OH)2
Dirty green precipitate
What colour is
|Fe(H2O)6|3+?
Yellow solution
What colour is Fe(OH)3?
Orange precipitate
What can transition metals act as homogeneous catalysts?
They have variable oxidation states
Why can transition metals act as heterogeneous catalyst?
Transition metals use D and S subshell electrons to form weak bonds to the reactants
Why are complexes coloured?
The Ligands cause d orbitals to split resulting in an energy gap
Electrons absorb light frequencies that match the energy gap to be able to get to the next from white light
The complimentary colour to the frequency absorbed is the colour of the complex
What are the advantages and disadvantages of hydrogen fuel cells over fossil fuels?
Advantages
Only water formed/ non polluting
Greater efficiency
Disadvantages
Difficult to store h2
Difficult to manufacture initially
Limited life cycle of h2 adsorber/absorber
What is standard electrode potential?
The potential difference of an electrochemical cell comprising a half cell combined with a standard electrode at standard conditions
1atm, 1 moldm-3, 298K
Give one use of chromium metal and state the property that makes it suitable
Stainless steel
Corrosion resistance
What are 2 examples of small ligands?
Water and ammonia
What is an example of large ligand?
Chlorine ions
What is a Brønsted-Lowry base?
Accepts H+ /protons
What do dilute ammonia and sodium hydroxide solution act as when reacting with transition metals?
Brønsted-Lowry bases
What happens when excess ammonia solution is added to copper metal ions (not in iron)?
Ligand substitution
4ammonia Ligands and 2 water
What happens when dilute ammonia or sodium hydroxide is added to fe or Cu?
Have 2 OH Ligands and 4water
Discuss two advantages and two disadvantages of using hydrogen fuels cells for energy
rather than using fossil fuels.
advantages:
only H2O formed/ non-polluting
greater efficiency
disadvantages:
H2 difficult to store
H2 difficult to manufactured initially /
limited life cycle of H2 adsorber/absorber
Define the term standard electrode potential.
potential difference (of electrochemical cell)
comprising of a half cell combined with a standard
hydrogen electrode 1
1 atm, 1 mol.dm–3
, 298K
what does it mean is a substance has a really positive standard electrode potential?
it is a strong oxidising agent
in an electrochemical cell in which direction do electrons flow?
towards the half cells with the more positive standard electrode potential
why does a more positive electrode potential make a better oxidising agent?
they have a greater tendancy to gain electrons
why might a redox reaction in an electrochemical cell not occur?
electrode potenrial may be too small, rate is too slow, not enough activation energy, not standard conditions
how can you use colorimetry to find the concentration a substance and the rate
choose filter with complementary colour to the substance you are trying to measure the concentration of
make up stand solutions of coloured solutions
zero the colorimeter with water
measure absorbance of each standard solution
plot calibration curve (absorbance against concentration)
measure the absorbance of the unknown sample at certain times throughout the reaction
use graph to read off each concentration for each absorbance measured
plot concentration against time and find rate
why does iron corrode in the centre of a water droplet not at the edge?
the oxygen concentration is at its lowest here
what can electrochemical cells be used for?
to measure concentration of ions in a solution
