General Chemistry - Electrochemistry

Chapter 12 MCAT

Electrochemical cells

contained systems in which oxidation reduction reaction occurs

Galvanic and concentration cells

spontaneous reaction

electrolytic cells

nonspontaneous reaction

Electrodes

where oxidation and reduction take place

anode

where oxidation occurs

cathode

where reduction occurs

electromotive force

corresponds to the voltage or electrical potential difference of the cell

Emf is positive

releases energy and spontaneous

emf negative

absorb energy and nonspontaneous

cell diagram

shorthand notation representing reactions in electrochemical cells

Electrolysis

redox reaction driven by an external voltage source, in which chemical compounds are decomposed

Concentration Cell

The electrodes are chemically identical

Rechargable cell

cell ufnctions as both a galvanic and electrolytic cell

Surge current

an above average current transently released at the beginning of the discharge phase, it wanes rapidly until stable current is achieved

Energy density

measure of a battery ability to produce power as a function of its weight

Lead Acid batteries

when discharging, consist of a Pb anode and a PbO2 cathode in a concentrated sulfuric acid solution. When charging the PbSO4 plated electrodes are dissociated to restore the original Pb and PbO2 electrodes and concentration the electrolyte, these cells have low energy density

Nickel Cadmium Batteries

When discharging consist of a Cd anode and a NiO cathode in a concentrated KOH solution. When chargin the NiCOOH and Cd OH2 plated electrodes are dissocated to restore the original Cd and NiO(OH) electrodes and concentrate the electrolyte. These cells have a higher energy density than lead acid batteries

Nickel Metal Hydride

Batteries have more or less replaced Ni Cd batteries because they have higher energy density and more cost effective and are significantly less toxicx

Reduction Potential

tendency of a species to gain electrons and be reduced