General Chemistry Ch. 12 – Electrochemistry

anode vs. cathode

flow of current vs. flow of electrons

oxidation vs. reduction

cathode to anode vs. anode to cathode

electromotive force

the voltage or electrical potential difference of an electrochemical cell

+ emf = -?G

– emf = +?G

galvanic cell
house spontaneous reactions with a positive emf

In a cell diagram which is the anode/cathode?

What do the lines denote?

 

 

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electrolytic cell
nonspontaneous reaction with negative emf; half reactions are not separated; commonly used in industry
What is Faraday’s constant and what does it represent?
105 C/mol e ; represents the charge contained in one mole of electrons
What is the electrodeposition equation and what does it mean?

mol M = It/(nF)

mol M is the amount of metal ion being deposited at an electrode

I is current

t is time

n is the number of electron equivalents for a specific metal ion

F is the Faraday constant

What are the distinguishing features of a concentration cell?
It is a specialized galvanic cell in which the electrodes are chemically identical. The current is generated as a function of the concentration gradient established between the two solutions surrounding the electrodes.
rechargeable cells

act as voltaic and electrolytic cells; as they discharge they act voltaic and as they recharge they act electrolytic

Examples are nickel-cadmium and lead-acid batteries

What equation relates Gibbs free energy and emf?

?Go = -nFEocell

G is the standard change in free energy

n is the number of moles of electrons exchanged

F is the Faraday constant

E is the standard emf of the cell

In electrolytic and voltaic cells what charge is the anode and cathode designated in each instance?

What way do electrons flow?

Where do oxidation and reduction occur?

  • In voltaic cells the anode is negative and the cathode is positive. In electrolytic cells it is the opposite.
  • Electrons always flow away from the anode.
  • Anode is always oxidation and cathode is always reduction.

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