14 - Redox II Flashcards
what is the standard electrode potential?
the potential obtained (tendency to release eletrons) when a metal is placed in a 1M solution of its ions at 298 K, or 100kPa of gases. relative to hydrogen
what is the standard hydrogen electrode made up of
hydrogen gas at 100kPa coming in, platinum electrode in solution containing hydrogen ions at 1 moldm-3
why is a reference electrode needed?
can only measure a potential DIFFERENCE
what does a positive E° value mean?
substance is more easily reduced and will gain electrons
what does a negative E° value mean?
substance is more easily oxidised and will lose electrons
how do you measure electrode potentials of metals/non-metals in their aqueous solutions?
half cell with solid metal electrode in its aqueous solution, connected by salt bridge of KNO3 to hydrogen half cell with platinum electrode in H+ solution with H2 gas
hwo do you measure electrode potentials of ions of the same element with different oxidation numbers
mixture of 1M solutions of each solution with a platinum electrode, connected by salt bridge of KNO3 to hydrogen half cell
conventional cell representation
- most negative potential goes on the left
- most oxidised species from each half cell goes next to the salt bridge
- state symbols always shown
how to find E° cell value
right hand cell - left hand cell, or most positive - most negative
how do you know if a reaction is thermodynamically feasible?
if the E° value is positive
what is E° directly proportional to?
total entropy change (ΔS total) and lnK
