Electrochemical cells and electrode potentials Flashcards
(27 cards)
What does a more positive E tell you?
it is a stronger oxidising agent
What does a more negative E tell you?
it is a stonger reducing agent
What is the standard electrode potential?
the emf (V) measured when a half cell is connected to a standard hydrogen half-cell under standard conditions
What is the role of the electrodes?
allows the flow of e-
What electrode is used for gases and when there is no solid metals present? and why?
platinum electrode Pt
it is inert = unreactive
How can you find the standard electrode potential of a reaction?
connect the half-cell containing the respective reaction to a standard hydrogen half cell
In what direction do electrons flow in terms of the value of E?
e- flows to the reaction with the more positive standard E
from the negative electrode to the positive electrode
What is the role of the salt bridge?
balances the charge of ions in the half-cells by allowing the controlled movement of ions between the two solutions
What is electroplating?
plating an electrode in solid metal
What need to be on a electochemical cell diagram?
the electrodes must be dipped in solution
salt bridge must be in solution and labelled
label the direction of e-
which electrode is recieving e- = positive and negative electrode labelled
standard conds
voltmeter reading
What are the standard conditions?
1 atm
298K
1 moldm-3
How is a salt bridge made?
a piece of filter paper soaked in potassium nitrate solution
What is a potential difference?
the difference in energy between two points in a circuit
At which electrode does reduction happen?
positive electrode
At which electrode does oxidation happen?
the negative electrode
What is the standard cell potential?
the difference between standard E values
What does a more positive standard E value tell you?
the more likely that half equation will run forwards in the direction of reduction (e- gained)
What will happen if you increase the concentration of reactants on the left of the reaction? and what will this do to the standard E value?
the equilibrium will shift to the right - so reduction is more favoured and the standard electron potential will become more positive
What are the 2 limiting factors of standard electrode potential values?
not under standard conds
rates of reaction
How does a high activation energy affect the standard electrode potential?
high Ea may prevent a reaction from happening or making it very slow, therefore it may not reach equilibrium
standard E values are only a prediction of what could happen
What is a storage cell?
an electrochemical cell where the voltmeter is replaced by an electrically powered device
How can a cell be recharged?
possing a current through the cell in the opposite direction to the normal current = drives reactions in reverse and regenerated the reactants
What is a fuel cell?
an electrochemical cell which used the energy released by reaction of fuel with oxygen to generate a voltage
What is the cell potential of a hydrogen-oxygen fuel cell?
1.23 V
