Chem / Phys: Oxidation & Reduction & Batteries Flashcards
A species with a higher reduction is more likely to be ___.
Reduced
A species with a lower reduction potential (more negative) is more likely to be ___.
Oxidized
If the amount of electrons being transferred in an electrochemical cell changes, do you have to account for that in your calculation of the cell’s EMF?
no! standard reduction potentials’ values come from their chemical identity, and not how much of them are present
___ occurs at the anode, and ____ occurs at the cathode. Always.
Oxidation ; Reduction
For a ___ cell, the reduction potential of the cathode has to be bigger than that of the anode.
Galvanic (spontaneous reactions)
When do concentration cells stop working? Note that they use two electrodes made of identical materials to make the cathode and the anode.
When the concentrations (ion gradients) of both electrolyte solutions are equal and no net change occurs (think of a neuron membrane at equilibrium)
What kind of cell breaks up ionic compounds into their composing ions?
Electrolytic Cell
Electrons flow from the ___ to the ___ in every type of electrochemical cell.
Anode to Cathode
___ ___ are made of inert electrolytes in Galvanic Cells .
Salt Bridges
What kind of electrolytes make up salt bridges in Galvanic cells?
SALTS SALTS SALTS (look for ionic compounds) you should look for strong electrolytes, like salts that will completely dissolve in solution. They’re called “inert electrolytes” because they neutralize charge without interfering with the battery reactions
What two factors determine a reaction’s equilibrium constant?
the identity of species in the reaction, and the temperature
concentration or quantity of those species has nothing to do with it, as the equilibrium constant is a ratio at equilibrium
Ecell (standard) is determined by what?
the identity of electrodes, not how much of those electrodes are there
Real quick: if the surface area that a reaction occurs on increases, the amount of reaction occurring at once will increase
YES
Where do electrons travel in a battery?
they go from one electrode into the wire and out the other electrode.
True / False: if oxidation decreases for some reason in a reaction, then that reaction’s E(oxidation) decreases.
True!
When Eox decreases, Ered ___ for that same reaction.
increases
What type of battery has characteristically low Energy density?
Lead-Acid Batteries
The ___ ___ of a Ni-Cd battery is high, so it can store more charge per mass than other batteries.
Energy Density
The electrodes of a __ __ battery can discharge through a circuit when they are fully charged.
Ni-Cd
What is “Surge Current”
the initial burst of current seen in some batteries
Can you increase a battery’s surge current by overcharging it?
no, running additional current into a charged battery the electrodes can’t store any more charge.
What is overcharging in terms of batteries?
continuining to try and run current into a battery even though the electrodes are fully charged and in their original states
Why can you overcharge Ni-Cd batteries without fear of hurting them?
once a Ni-Cd battery’s electrodes are charged and reverted to their original state they will stop accepting any more electrons
During the recharge cycle, Ni-Cd cells will accept current to revert their electrodes into their original compositions until the ___ and ___ electrodes are pure. This stops when Cd(OH)2 runs out and no more electrons can be accepted.
Cd ; NiO(OH)
