3.1 - Redox + standard electrode potential Flashcards
Oxidation
loss of electrons
Reduction?
gain of electrons
Oxidising agent?
Species that oxidises another species but is itself reduced
Examples of oxidising agents?
Potassium Dichromate
Potassium Permangenate
Concentration Sulphuric acid
What colour does Potassium Dichromate turn?
Orange to Green
What colour does Potassium Permangenate turn?
KmnO4
Purple to colourless
What is the strongest oxidising agent?
Fluorine
What is a reducing agent?
Reduces another species but itself oxidised
Examples of Reducing agent?
Sodium Tetrahydridoborate(III)
Lithium tetrahydridoaluminate(III)
Sodium and ethanol
Sodium Tetrahydridoborate(III)?
NABH4
Lithium tetrahydridoaluminate(III)
LIAlH4
must be dissolved in ethoxyethane
anhydrous conditions
no water
Sodium and ethanol?
Na+C2H5OH
Diagram of a cell
What are the standard conditions?
25 degrees / 298K
1 atm/1.01x10^5
conc of 1 moldm-3
what is the equation of Copper?
Cu2+ + 2e- —– Cu(s)
EMF = 0.34 V
what is the equation of zinc?
Zn2+ + 2e- —– Zn(s)
EMF = 0.76V
Example of oxidation?
Zn(s)—- Zn2+(aq) + 2e-
What does faesibility mean?
possibility
How do you know if its faesible?
if it is positive
Cu2++2e- + Zn(s) —- Cu(s) + ZN2+ + 2e-
Cu2+ + Zn(s) —- Cu(s) + ZN2+(aq)
What is SO42- ( big 4 little -2) in this reaction?
a spectator ion
what is a celldiagram?
is a short hand picture of the diagram of the cell
what is the cell diagram?
What is the standard hydrogen electrons used for?
to work out the EMF of the other half cells
Equation for This
2H+ + 2e- —- H2
E value= 0.00 as we dont want it to affect the others by all means
Equation
2H+ + 2E- —- H2
Zn (S) —- Zn2+ + 2e-
2H+ is the oxidising agent and Zn(s) is the reducing agent
What is a redox reaction?
when both reduction and oxidation take place at the same time
what in an example of a redox reaction?
in the oxidation of alcohol
What is the reduction of a nitride?
C=N ( 3 equal lines)
Example of the reduction of a carboxylic acid, an aldehyde + ketone?
reduction of a nitrobenzene
How does the fuel cell work?
Fuel cells convert chemical energy stored in the fuel (hydrogen) into the electrical energy
(H2—2H+2e-)
These produce electrons which flow in external circuit
Hydrogen is a more efficient at releasing energy than traditional fossil fuels
The electrons are made of Platinum as it is inert
Hydrogen is passed over at the platinum electrode where platinum acts as a catalyst
what happens at the anode?
electrons are lost
H2-2H+ + 2e-
Oxidation takes place
the hydrogen ions pass through a semi permeable membrane to reach the cathode
what happens at the cathode?
electrons are gained and react with hydrogen ions + oxygen to form water
What does catalyst means?
substance which lowers the activation energy and provides an alternative pathway for the reaction to proceed
What are advantages?
Only produces water as a waste product (no Co2 emissions )
less energy is wasted as heat - more efficient
Hydrogen gas can be produced by burning fossil fossil fuels
Hydrogen is a renewable source of energy
what are disadvantages?
Highly flammable + must be stored in a pressured tank which is expensive to produce
Hydrogen as a fuel can only produced by traditional methods
fuel cells operate at lower temperatures of 80 degrees but need a catalyst + all transition metals are expensive
