Electrochem Flashcards
(18 cards)
define reduction, oxidation
Reduction- gaining elect
ox - losing elect
How to know if something is spontaneous or not based on half react table
if the oxidizing agent is higher than the reducing agent then it is spont
How to know if reduct or ox based on half reaction
elect on right = ox
elect on left = reduct
What are the steps to balance redox react in basic or acidic solution
(OTHER)
- get half reaction eq (figure out which is ox or reduct)
- balance Redox react, start with not O or H
- add H2O to balance out O
- add H+, if basic then add OH on both sides to turn it into H2O
- add e - to balance carge
what are the oxidation nums for O, H in diff situations (7)
0 - diatomic, single atom compounds
+1 - H+ usually
-1 = H+ in hydride (ionic)
-2 - O usually
-1 - O in peroxie
+2 - O with fluorine
charge - ions
How to know if reduct or ox from ox num
if increase - ox
if decrease - reduct
if no change then redox reaction
How to balance reaction using ox nums
write unbalanced eq
determine ox num
determine how much it changes by
get lowest common multiple
multiply ox and reduct elements to get LCM (only add coeffs to left side)
balance other elemt on right
What are the main parts of galvanic cell (5)
electrolyte - solution needed
salt bridge - allows diffusion of ions, keeps charge balanced
cathode - where reduction
anode - where ox happens
electrical conductor - allows flow of elect from redox reactons
What is the salt bridge used for
keeps the solutions electrically Neutral as the electrons leave the anode and go to cathode
otherwise deposites would form of ions
charge of solutio n would change
What is inert electrode
electrode made with non reactant or product of the cell reaction
How does a galvanic cell work
converts chem eng to elect eng
redox reactions are separated
half reactions happen in separate beaker
electrons go from anode to cathode
What is shorthand notation for galvanic cell
anode|electrolyte||electrolyte|cathode
what is electric potential of cell (+ eq)
diff between elect pot of anode and cathod
E = E(cathode) - E(anode)
must be reduction potential of each, not oxidaton
in volts
calc cell pot of
2Ag+ + Zn -> 2Ag + Zn2+
if Ag E = 0.7996
Zn2+ E = -0.7628
cathode- anode (reduction potential)
1.5624
DO NOT CONSIDER COEFFICIENTS IN STANDARD CELL POT CALCs
Why do you not look at coeff wen calculating standard cell pot?
molar concentration does not affect how quickly electrons flow
voltage measures eng transfer in redox react
What does high reduct pot values mean for element
high tendency to gain elect
strong oxidizing agents
more likely to undergo reduction
if low reduct pot
mainly ox reaction
How is hydrogen used as a standard ref for cell pot to determine voltage of other things
its standard reduction pot is 0 all other elements are pos or neg depending on if they reduce easier
How to use overall cell pot to predict sponentaity
if E(cell) > 0 - spont
if E(cell) < 0 - not spont
