Chem / Phys: Oxidation & Reduction & Batteries

Question 1

A species with a higher reduction is more likely to be ___.

Answer 1

Reduced

Question 2

A species with a lower reduction potential (more negative) is more likely to be ___.

Answer 2

Oxidized

Question 3

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?

Answer 3

no! standard reduction potentials’ values come from their chemical identity, and not how much of them are present

Question 4

___ occurs at the anode, and ____ occurs at the cathode. Always.

Answer 4

Oxidation ; Reduction

Question 5

For a ___ cell, the reduction potential of the cathode has to be bigger than that of the anode.

Answer 5

Galvanic (spontaneous reactions)

Question 6

When do concentration cells stop working? Note that they use two electrodes made of identical materials to make the cathode and the anode.

Answer 6

When the concentrations (ion gradients) of both electrolyte solutions are equal and no net change occurs (think of a neuron membrane at equilibrium)

Question 7

What kind of cell breaks up ionic compounds into their composing ions?

Answer 7

Electrolytic Cell

Question 8

Electrons flow from the ___ to the ___ in every type of electrochemical cell.

Answer 8

Anode to Cathode

Question 9

___ ___ are made of inert electrolytes in Galvanic Cells .

Answer 9

Salt Bridges

Question 10

What kind of electrolytes make up salt bridges in Galvanic cells?

Answer 10

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

Question 11

What two factors determine a reaction’s equilibrium constant?

Answer 11

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

Question 12

Ecell (standard) is determined by what?

Answer 12

the identity of electrodes, not how much of those electrodes are there

Question 13

Real quick: if the surface area that a reaction occurs on increases, the amount of reaction occurring at once will increase

Answer 13

YES

Question 14

Where do electrons travel in a battery?

Answer 14

they go from one electrode into the wire and out the other electrode.

Question 15

True / False: if oxidation decreases for some reason in a reaction, then that reaction’s E(oxidation) decreases.

Answer 15

True!

Question 16

When Eox decreases, Ered ___ for that same reaction.

Answer 16

increases

Question 17

What type of battery has characteristically low Energy density?

Answer 17

Lead-Acid Batteries

Question 18

The ___ ___ of a Ni-Cd battery is high, so it can store more charge per mass than other batteries.

Answer 18

Energy Density

Question 19

The electrodes of a __ __ battery can discharge through a circuit when they are fully charged.

Answer 19

Ni-Cd

Question 20

What is “Surge Current”

Answer 20

the initial burst of current seen in some batteries

Question 21

Can you increase a battery’s surge current by overcharging it?

Answer 21

no, running additional current into a charged battery the electrodes can’t store any more charge.

Question 22

What is overcharging in terms of batteries?

Answer 22

continuining to try and run current into a battery even though the electrodes are fully charged and in their original states

Question 23

Why can you overcharge Ni-Cd batteries without fear of hurting them?

Answer 23

once a Ni-Cd battery’s electrodes are charged and reverted to their original state they will stop accepting any more electrons

Question 24

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.

Answer 24

Cd ; NiO(OH)