Experiment V Flashcards
mnemonic to remember electrochemistry electron rules
LEO is a GERC
spontaneous reaction
SOA and SRA are on the left side of the equation
non-spont. reaction
SOA and SRA are on the left side of the equation
reduced form of a half reaction
(electron on left side)
Ag+ + e- = Ag
oxidized form of a half reaction
electron on right side
Ag = Ag+ + e-
galvanic/voltaic cell
cell in which current is generated from spontaneous reactions
Electrons flow in what direction
negative to positive
salt bridge
allows for ion exchange but not wholesale mixing
cell voltage
measure of the driving force or the degree of spontaneity of the reaction
Halogen reaction general form
X2 + 2e- = 2X-
how does can halogens inform us about the spontaneity of reactions
Halogen are highly soluble in Hexane, but not water. (like dissolves like)
Ions are highly soluble in water but not hexane.
If hexane changes colour, it means that there is I2 present in it and thus the reaction proceeded
If it does not change colour, it means that there is still only I- present and thus the reaction did not proceed
Ecell of a spontaneous reaction
positive
Ecell of a non spontaneous reaction
negative
What colour would iodine change the colour of hexane to
reddish purple - purple
What colour would chloring change the colour of hexane to
light yellow
voltage
difference between the E° of half cells
E°
concentration of dissolved species = 1M
pressure of gases = 1M
if you have a non-standard cell, what do you use
use Nernst equation
how is E° cell affected by multiplying half-cell by integer
it is not, it is an intensive property and thus unaffeced
How should you look at the data table if you want to make a spontaneous cell
you need a positive final number, so take the cathode below the anode
greater positive E
cathode
greater negative E
anode
Lab V part 3 reaction of precipitate
2Ag+ + S2O3^2- = (Ag2)S2O3
and then
(Ag2)S2O3 decomposes into Ag2S
what colour is (Ag2)S2O3
white/cream precipitate
what colour is Ag2S
black precipitate
ICE table rules for 2Ag+ + S2O3^2
If ppt forms, reaction goes to 100%
If no ppt forms, ICE table has a stoich shift, then a small change to equilibrium
what colour is Ag(S2O3)2^3-
colourless and clear. not a precipitate
cell shorthand for a cell that produces precipitate
Ag(s) | Ag+(? M) ∥ Ag+(1 M) | Ag(s)
Why is the Ag+(?M) the anode
Because Ag+ is the concentration of of ions after the formation of the complex ion, thus there is a lower concentration of them in the solution
This means the Ag electrode will oxidized, so that Ag+ concentration increases
The extra e- formed during the oxidation, travels to the cathode
Why is the Ag+(?M) the anode, when forming
Because the Ag+ is the concentration of ions after precipitating, there is a lower concentration in the solution.
That means the Ag electrode will be oxidized, so that Ag+ concentration increases.
The extra e- formed during the oxidation, travel to the cathode
