electrode potentia Flashcards
define half cell
A strip of metal dipped into a solution of its own ions can be called an ELECTRODE
Why is KNO3 a suitable solution for a salt bridge
KNO3 is unreactive with the elecrodes AND the ions are free to mov
where is the most reactive metal in a circuit
left
Why might the current produced by a cell fall to zero after some time
all reactants used up
What will happen to a cell once the reactants are used up?
stops working OR starts to leak
where does oxidation always occur
left negative electrode
when at Pt electrodes used
when there is no solid metal in the reaction, such as when there are metal ions of two different charges in the same solution
Why is platinum a suitable electrode
unreactive and conducts electricity
conditions for standard electrode
100kPa, 1moldm-3, Pt electrode, 298K
The voltage of the Standard Hydrogen Half Cell is defined as
zero
vertical solid lines indicate in a circuit a
phase boundary
Which is the strongest oxidising agent(SO
strongest oxidising agent on the left will have most positive standard electrode potential
Which is the weakest reducing agent (WR)
weakest reducing agent on the right will have most positive standard electrode potential
if an ion is more positive then
it will react
how do you work out EMF
more positive - least positive
Give an environmental advantage of using rechargeable cells
Metals are reused
Give an environmental disadvantage of using rechargeable cells
Mains electricity is used to recharge, which may come from combusting fossil fuels, which releases CO2(
Q: The cell made of the systems Mg/Mg2+ and Fe2+/Fe under standard conditions has an e.m.f. of 1.93 V.
Deduce how the e.m.f. of the cell Mg/Mg2+ and Fe2+/Fe changes when the concentration of Mg2+ is decreased. Explain your answer. (3 marks)
Use the data below;
E/ V
Mg2+(aq) + 2e– Mg(s) –2.37
Fe2+(aq) + 2e– Fe(s) –0.44
When Mg2+ is decreased, the equilibria shifts left.
So the Evalue at the Mg2+ electrode becomes more negative, as more electrons are made
e.m.f. = more positive – least positive = -0.44 – (-2.37) = 1.93 V
So after the Mg2+ is increased the -2.37 could become around -2.40,
e.m.f. = -0.44 – (-2.40) = 1.96 V
Advantages of using fuel cells for energy instead of fossil fuels.
- Major advantage; Greater efficiency than burning hydrogen in a combustion engine
- Less-polluting as water is the only product
Disadvantages of using fuel cells for energy instead of fossil fuels.
- H2 is difficult to store
- Fossil fuels are combusted to produce the hydrogen, which releases carbon dioxide
Advantages of fuel cells compared to other types of cell
Voltage is constant, as fuel and oxygen is supplied constantly so concentrations of reactants remain constant
State the meaning of the term electrochemical series
(List of) electrode potentials/ in (numerical) order
