Electrochemistry

Question 1

Oxidation number of hydrogen in most compounds

Answer 1

+1

Question 2

Oxidation number of oxygen in most compounds

Answer 2

-2

Question 3

Oxidation number of fluorine in any compound

Answer 3

-1

Question 4

Elemental species have an oxidation number of

Answer 4

0.

Question 5

Elemental ions have oxidation numbers

Answer 5

equal to their charge.

Ex. In Fe³⁺, iron has an oxidation number of +3

Question 6

All oxidation numbers of each individual atom in a compound must add up to

Answer 6

the charge on the compound.

Question 7

Group 1A metals oxidation state in all compounds

Answer 7

+1

Question 8

Group 2A metals oxidation state in all compounds

Answer 8

+2

Question 9

Meaning of LEO says GER

Answer 9

Loss
Electrons
Oxidized

Gain
Electrons
Reduced

Question 10

Oxidation always occurs at the

Answer 10

anode. (Red cat / an ox)

Question 11

Reduction always occurs at the

Answer 11

cathode. (Red cat / an ox)

Question 12

Electrons flow in what direction in an electrochemical cell?

Answer 12

Anode to cathode (FAT Cat)

Question 13

Which electrode is sometimes found to lose mass in an electrochemical cell?

Answer 13

Anode (FAT Cat)

Question 14

Which electrode can have matter accumulate at the electrode?

Answer 14

Cathode (FAT Cat)

Question 15

Cations travel through the salt bridge to which half-cell?

Answer 15

Cathodic

Question 16

Anions travel through the salt bridge to which half-cell?

Answer 16

Anodic

Question 17

How does the salt bridge complete the circuit in an electrochemical cell?

Answer 17

Ions travel through salt bridge

Note: Electrons do NOT freely travel through the salt bridge.

Question 18

When you reverse a reaction, what do you do to E°?

Answer 18

Change the sign (pos to neg or neg to pos)

Question 19

When you change the coefficients of a reaction, what happens to E°?

Answer 19

NO CHANGE

Question 20

Formula for E°_cell from half-reaction potentials

Answer 20

E°_cell = E°_red + E°_ox

Question 21

When adding half-reactions, what has to happen?

Answer 21

Electrons must cancel out

Question 22

For a galvanic/voltaic cell, the half-reaction with the more positive E*°_red will occur at the

Answer 22

cathode.

Question 23

For a galvanic/voltaic cell, the E*°_cell must be

Answer 23

positive.

Question 24

When calculating ΔG°_rxn from E°_cell or vise-versa, ΔG*°_rxn must be in

Answer 24

J NOT kJ.

Question 25

When calculating ΔG°_rxn from E*°_cell or vise-versa, n is the

Answer 25

moles of electrons transferred per mole of rxn.

Question 26

What is considered to be standard conditions?

Answer 26

Gases at 1 atm partial pressure
Concentrations at 1 M
Temperature at 298 Kelvin

Question 27

At non-standard conditions, if Q is ______ than one, E is less than E°.

Answer 27

Greater

Question 28

At non-standard conditions, if Q is less than one, E is _______ than E°.

Answer 28

Greater (more reactants, so more charged)

Question 29

As Q approach K for a galvanic/voltaic cell, what happens to the voltage?

Answer 29

The voltage approach zero

Equilibrium is where batteries go to die!

Question 30

K for galvanic/voltaic cells reactions is usually

Answer 30

a huge number (very product favored and goes to completion).