electrochemistry
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define electrolyte
an aqueous or ionic compound that is conducting electricity
what metal out of copper or magnesium is more reactive
magnesium as it loses electrons more
which species is more likely to be reduced Pb4+ + 2e- ⇌ Pb2+ Electrode potential = 1.67 v 2H+ + 2e- ⇌ H2 Electrode potential = 0.00 v
Pb4+ as the electrode potential is the most positive so most likely to gain electrons
which species is more likely to be oxidised Cl2 + 2e- ⇌ 2Cl- Electrode potential = 1.67 v Mg2+ + 2e- ⇌ Mg Electrode potential = -2.36 v
Mg as the electrode potential is most negative so most likely to lose electrons
explain the procedure for standard cell representation
• reverse direction of the half equation with most negative electrode potential • most negative half equation goes on left, most positive goes on the right • double line indicates a salt bridge || • electrodes go on the outside • phase changes are shown by a single line | • species in the same phase are separated by a comma (,)
how do you calculate cell emf
cell emf = right electrode potential - left electrode potential
how do electrons flow in an electrochemical cell
electrons flow from the most negative electrode to the most positive electrode (tends to be from left to right)
do electrons flow when there is a voltmeter in the circuit
electrons do not flow when a voltmeter is used in the circuit
what happens to emf over time and why
emf decreases as the reactants get used up and the cell discharges
what factors affect the cell emf of an electrochemical cel
concentration temperature
where does the hydrogen reference electrode always go
on the left
what is the emf of the circuit with the hydrogen reference electrode equal to
the emf of the circuit with the hydrogen reference electrode equal to the electrode potential of the half cell it is connected to
what are the 3 standard conditions associated with the hydrogen reference electrode
H2 gas at 100 kPa 1.00 mol dm-3 HCl 298 K
what happens if the change pushes the equilibrium towards X in terms of electrode potential X+ + e- → X
if changes pushes equilibrium towards X then electrode potential becomes more positive
what happens if the change pushes the equilibrium towards X+ in terms of electrode potential X+ + e- → X
if change pushes equilibrium towards X+ then electrode potential becomes less positive (more negative)
what are the 4 steps to combining half equations
• reverse direction of equation with most negative electrode potential • multiply equations so that the number of electron balance • combine all reactants and all products • cancel out all species that are the same on both sides
define electrochemical series
a list of half equations in order of electrode potential
what is the strongest reducing agent in the electrochemical series
the species on the right with the most negative electrode potential (as it is most likely to be oxdised)
what is the strongest oxidising agent in the electrochemical series
the species on the left with the most positive electrode potential (most likely to be reduced0
What are species with a more negative electrode potential likely to do
species with a more negative electrode potential are able to reduce those with a more positive electrode potential
what are species with a more positive electrode potential likely to do
species with a more positive electrode potential are able to oxidise those with a more negative electrode potential
write the equations for the positive and negative electrode in a lithium ion cell
positive electrode Li+ + CoO2 + e- → Li+CoO2 - +1.01 v negative electrode Li → Li+ + e-
write an equation for the discharge of lithium electrochemical cell in an iron casing
Li+ + CoO2 → Li+CoO2 -