electrochemistry Flashcards
what is potential defined as in an electrochemical cell
how readily electrons are released by the metal therefore how good of a reducing agent it is.
how do you measure potential difference
connect the two electrodes and measure the potential difference between them - voltage-
what is an electrode
when a rod of metal is dipped into a solution of its ions
what is the purpose of a salt bridge
completes the circuit
allows ions to move through the solution
if it is more negative is it a better reducing or oxidising agent
reducing agent - it itself is loosing electrons causing another species to gain them
describe the standard hydrogen electrode
298K 100Kpa
hydrogen ion conc = 1.00moldm-3
hydrogen gas is bubbled into a solution of hydrogen ions
electrical contact is made with an unreactive platinum rod - to increase surface area to allow the reaction to proceed rapidly
what si the potential of the standard hydrogen electrode
ZERO
which direction do electrons flow in an electrode
more negative to more positive
which conditions will change emf values
conc of ions
- temperature
-
what si the equation for emf
positive - negative
BE HAPPY
when commenting on feasibility of a reaction what should you think about
is there flow from the most negative to the most positive
you can check E naught values
how does a non-rechargeable cell work
chemicals are used up over time, once one or more of the chemicals have been used up the cell is flat and the emf is 0
what happens to the emf of a non rechargeable cell over time
drops until it reaches 0
how are rechargeable cells rechargeable
by supplying an external current and regenerating the chemicals
- reactions are reversible BTW
describe fuel cells
they have a continuous supply of chemicals into the cell and so neither run out nor run out of charge.
NEED A CONSTANT SUPPLY OF CHEMICALS
what does the graph of emf against time look like for a fuel cell
straight line never drops
what is an advantage if using a non-rechargeable cell
cheap
what is a disadvantage of using a non-rechargeable cell
waste issues
what is an advantage of using rechargeable cells
less waste
cheaper in the long run
what is a disadvantage of using a rechargable cell
waste issue at end of life
what is an advantage of using a hydrogen-oxygen fuel cell
only waste product is water = environmentally friendly
- very efficient
- do not need recharging
-
what are some disadvantages of using a hydrogen-oxygen fuel cell
need a constant supply of chemicals
- hydrogen is very flammable
- h is made using fossil fuels
- VERY EXPENSIVE TO RUN
