Electrode Potentials & Electrochemical Cells Flashcards
What is the purpose of a salt bridge?
to allow the ions to move between half cells
Identify an ionic compound that could be used in a salt bridge
Potassium nitrate
What are electrochemical cells used as?
a commercial source of electrical energy
What do lithium ion cells power?
laptop and mobile devices
Why is lithium used in the lithium cells?
because it has a very low density and relatively high electrode potential
What do lithium cells consist of?
- a positive lithium cobalt oxide electrode
- a negative carbon electrode
- a porous polymer membrane electrolyte
What is advantageous about lithium cells using polymer electrolyte?
It cannot leak since it is not a liquid or paste
What is the half-cell equation at the negative electrode (in a lithium cell)?
Li <-> Li+ + e-
What is the half-cell equation at the positive electrode (in a lithium cell)?
e- + Li+ + CoO2 <-> Li+(CoO2)-
What is the full cell equation of a lithium cell?
Li + Li+ + CoO2 <-> Li+ + Li+(CoO2)-
How can a lithium cell be recharged?
a current has to be applied over the cell which forces electrons to move in the opposite direction - this causes the reaction to reverse, recharging the cell
What is a fuel cell?
a type of electrochemical cell that is used to generate an electrical current without needing to be recharged
What is the most common type of fuel cell?
the Hydrogen fuel cell
What does the Hydrogen fuel cell use to generate a continuous current?
a continuous supply of hydrogen and oxygen from the air
Why is the Hydrogen fuel cell seen as being much more environmentally friendly?
the reaction that takes place produces water as the only waste product
What are the downsides to Hydrogen fuel cells?
- the high flammability of hydrogen
- they are expensive to produce meaning they are not yet used too commonly
Increasing the concentration of the solutions used in the electrochemical cell, changes the EMF of the cell how?
makes the cell EMF more positive as fewer electrons are produced in the reaction
Increasing the pressure of the cell will change the EMF of the cell how?
will make the cell EMF more negative as more electrons are produced
On an electrochemical series (becoming more negative in standard potential as you go down), where is the strongest oxidising agent located?
top left
On an electrochemical series (becoming more negative in standard potential as you go down), where is the strongest reducing agent located?
bottom right
State the meaning of the term electrochemical series.
A list of electrode potentials in numerical order
