Electrochemistry

Question 1

What can I assume about the Ecell of a cell that charges a battery?

Answer 1

The Ecell is larger than the battery charge

Question 2

What is Ecell of a concentration cell?

Answer 2

Always 0

Question 3

How to determine which species will get reduced in an electrochemical cell?

Answer 3

galvanic: one with highest Ered (galvanic if the battery powers something)
electrolytic: one with the lowest Ered

Question 4

What is important to remember when calculating Ecell?

Answer 4

No need to switch the sign for the reaction to be the one happening, and no need to multiply to have the same number of electrons

Question 5

What does positive Ecell mean?

Answer 5

Spontaneous reaction

Question 6

What does negative Ecell mean?

Answer 6

Nonspontaneous reaction

Question 7

How can I determine which compound will have the highest conductivity?

Answer 7

Look at how many ions the compounds will dissociate into

Question 8

How to calculate the real Ecell when the conditions are not standard? What is this equation called?

Answer 8

Ecell = Ecell (standard) - 0.06/n . log Q

Q = reaction quotient

Nernst equation

Question 9

What is the equation to calculate Delta G from the standard emf of a cell?

Answer 9

Delta G = -n.F.Ecell

Question 10

What is the electrodeposition equation? What does it represent? What to be careful about?

Answer 10

mol M = I.t / n.F

mol M = moles of metal
n = number of electron equivalents - BE CAREFUL ABOUT STOCHIO

Represents the amount of metal ion being deposited at a specific electrode

Question 11

What is the electron movement direction in ALL electrochemical cells?

Answer 11

Anode to cathode

Question 12

What is the current movement direction in ALL electrochemical cells?

Answer 12

Cathode to anode

Question 13

How to calculate voltage in a concentration cell?

Answer 13

Nernst equation:

E = 61.5 / z . log ([ion out]/[ion in])

Question 14

What type of cell is a concentration cell?

Answer 14

Galvanic

Question 15

Why can a Ni-Cd battery get overcharged without it being detrimental?

Answer 15

because it stops accepting electrons when electrodes are charged

Question 16

What is the purpose of the salt bridge?

Answer 16

The ions in the salt bridge do not participate in the reaction. The purpose of the salt bridge is not to supply reagents for the half-reactions, but rather to ensure that each side does not accumulate charge (and thereby creating a force to stop the reaction) → the ions flow into the compartments to equalize charge

Question 17

How to find out which species would work for a salt-bridge?

Answer 17

eliminate non-ionic species

Question 18

What dictates how many electrons will flow per unit time? Why?

Answer 18

The amount of exposure the electrodes have to the solution, because the reaction can only happen at the surface of the electrodes

Question 19

What is the other name for galvanic cell?

Answer 19

Voltaic

Question 20

At what electrode does deposition occur?

Answer 20

Cathode

Question 21

When can we use Ecell = Ered cat - Ered an

Answer 21

Standard conditions: 1 M, 1 atm, 25 degrees celcius

Question 22

What is the reaction happening in a lead-acid battery?

Answer 22

Pb (s) + PbO2 (s) + 2 H2SO4 –> 2 PbSO4 + 2 H2O

Question 23

How do you balance redox reactions in acidic conditions?

Answer 23

1. Balance oxygen by adding H2O
2. Balance number of Hs by adding H+
3. Balance charge by adding electrons

Question 24

How do you balance redox reactions in basic solutions?

Answer 24

First assume it is acidic
If that is not one of the answer choices:
1. replace all of the H+ with water and cancel out H2O molecules on each side
2. Add the same number of OH- on the other side

Question 25

What is the reaction happening in a nickel-cadmium battery?

Answer 25

2 NiO(OH) (s) + Cd + 2 H2O --> 2 Ni(OH)2 (s) + Cd(OH)2

Question 26

Why battery provides the better surge current?

Answer 26

Nickel-cadmium

Question 27

What is a surge current?

Answer 27

Periods of large current early in the discharge cycle

Question 28

What to do when asked to calculate the work output of a cell per mole of reactant?

Answer 28

Calculate Delta G!

Question 29

How to calculate the moles of oxidizing metal necessary to run the cell for a certain amount of time?

Answer 29

n = I.t/F Then look at how many electrons are released by each mole and divide n by that number

Question 30

To reverse the direction of current in a cell, what should be the voltage of the battery?

Answer 30

Higher than the Ecell of the cell

Question 31

Where do the cations of the salt bridge move to in a galvanic cell?

Answer 31

Cathode

Question 32

In a concentration cell, which electrode is the cell with the highest concentration?

Answer 32

Cathode

Question 33

In a concentration cell, which electrode is the cell with the lowest concentration?

Answer 33

Anode

Question 34

What are the rules for cell line notations?

Answer 34

Anode on the left | Cathode on the right

Question 35

What is the reduction potential of H+?

Answer 35

0