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MCAT Chemistry > Electrochemistry > Flashcards

Electrochemistry Flashcards

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1
Q

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

A

The Ecell is larger than the battery charge

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2
Q

What is Ecell of a concentration cell?

A

Always 0

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3
Q

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

A

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

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4
Q

What is important to remember when calculating Ecell?

A

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

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5
Q

What does positive Ecell mean?

A

Spontaneous reaction

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6
Q

What does negative Ecell mean?

A

Nonspontaneous reaction

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7
Q

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

A

Look at how many ions the compounds will dissociate into

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8
Q

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

A

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

Q = reaction quotient

Nernst equation

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9
Q

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

A

Delta G = -n.F.Ecell

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10
Q

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

A

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

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11
Q

What is the electron movement direction in ALL electrochemical cells?

A

Anode to cathode

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12
Q

What is the current movement direction in ALL electrochemical cells?

A

Cathode to anode

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13
Q

How to calculate voltage in a concentration cell?

A

Nernst equation:

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

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14
Q

What type of cell is a concentration cell?

A

Galvanic

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15
Q

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

A

because it stops accepting electrons when electrodes are charged

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16
Q

What is the purpose of the salt bridge?

A

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
Q

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

A

eliminate non-ionic species

18
Q

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

A

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

19
Q

What is the other name for galvanic cell?

A

Voltaic

20
Q

At what electrode does deposition occur?

A

Cathode

21
Q

When can we use Ecell = Ered cat - Ered an

A

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

22
Q

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

A

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

23
Q

How do you balance redox reactions in acidic conditions?

A
  1. Balance oxygen by adding H2O
  2. Balance number of Hs by adding H+
  3. Balance charge by adding electrons
24
Q

How do you balance redox reactions in basic solutions?

A

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
Q

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

A

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

26
Q

Why battery provides the better surge current?

A

Nickel-cadmium

27
Q

What is a surge current?

A

Periods of large current early in the discharge cycle

28
Q

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

A

Calculate Delta G!

29
Q

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

A

n = I.t/F

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

30
Q

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

A

Higher than the Ecell of the cell

31
Q

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

A

Cathode

32
Q

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

A

Cathode

33
Q

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

A

Anode

34
Q

What are the rules for cell line notations?

A

Anode on the left

Cathode on the right

35
Q

What is the reduction potential of H+?

A

0

MCAT Chemistry (17 decks)

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