Electrochemistry Flashcards Preview

MCAT Chemistry > Electrochemistry > Flashcards

Flashcards in Electrochemistry Deck (35):
1

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

The Ecell is larger than the battery charge

2

What is Ecell of a concentration cell?

Always 0

3

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

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

4

What is important to remember when calculating Ecell?

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

5

What does positive Ecell mean?

Spontaneous reaction

6

What does negative Ecell mean?

Nonspontaneous reaction

7

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

Look at how many ions the compounds will dissociate into

8

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

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

Q = reaction quotient

Nernst equation

9

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

Delta G = -n.F.Ecell

10

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

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

11

What is the electron movement direction in ALL electrochemical cells?

Anode to cathode

12

What is the current movement direction in ALL electrochemical cells?

Cathode to anode

13

How to calculate voltage in a concentration cell?

Nernst equation:

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

14

What type of cell is a concentration cell?

Galvanic

15

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

because it stops accepting electrons when electrodes are charged

16

What is the purpose of the salt bridge?

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

17

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

eliminate non-ionic species

18

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

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

19

What is the other name for galvanic cell?

Voltaic

20

At what electrode does deposition occur?

Cathode

21

When can we use Ecell = Ered cat - Ered an

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

22

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

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

23

How do you balance redox reactions in acidic conditions?

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

24

How do you balance redox reactions in basic solutions?

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

25

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

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

26

Why battery provides the better surge current?

Nickel-cadmium

27

What is a surge current?

Periods of large current early in the discharge cycle

28

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

Calculate Delta G!

29

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

n = I.t/F

Then look at how many electrons are released by each mole and divide n by that number

30

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

Higher than the Ecell of the cell

31

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

Cathode

32

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

Cathode

33

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

Anode

34

What are the rules for cell line notations?

Anode on the left
Cathode on the right

35

What is the reduction potential of H+?

0