Chapter 20 - Electrochemistry

Question 0

A species is oxidized when

Answer 0

It loses electrons

Question 1

What is transferred in electrochemical reactions?

Answer 1

Electrons from one species to another

Question 2

A species is reduced

Answer 2

When it gains electrons

Question 3

Oxidizing agent

Answer 3

What is reduced

Question 4

Reducing agent

Answer 4

What is oxidized

Question 5

Elements in their elemental form have an oxidation number of

Answer 5

Zero

Question 6

The oxidation number of a mono atomic ion is

Answer 6

The same as its charge

Question 7

Oxidation numbers of non metals

Answer 7

Tend to be negative

Oxygen is -2
Hydrogen is -1 when bonded to metal and +1 when bonded to nonmetal

Question 8

Oxidation number of halogens

Answer 8

-1 usually

Question 9

Sum of oxidation numbers in neutral compound

Answer 9

Equals 0

Question 10

Sum of oxidation numbers in a polytonal ion

Answer 10

Is the charge on the ion

Question 11

Half reaction method

Answer 11

1. Assign oxidation numbers
2. Write half reactions
3. Balance each half
   - balance elements other than O and H, balance O by adding water, balance H by adding H+, and balance charge by adding electrons
4. Multiply reactions by integers so tht the electron gained and lost is equal
5. Add reactions
6. Make sure balance in mass and charge

Question 12

Balancing in basic solution

Answer 12

Once eqn is balanced add OH to each side to neutralize the hydrogen ion and create water

Question 13

Voltaic cell

Answer 13

Setup where an external device is used to make electrons flow

Question 14

Oxidation in voltaic cells occur at

Answer 14

The anode (-)

Question 15

Reduction in voltaic cells occur at

Answer 15

The cathode (+)

Question 16

Salt bridge and movement of ions in voltaic cell

Answer 16

Salt bridge is used to keep the charges balanced

Cations move toward cathode
Anions move toward anode

Question 17

Electron flow in voltaic cell

Answer 17

Anode to cathode

Question 18

Electron flow in a redox reaction

Answer 18

Electrons only spontaneously flow from higher to lower potential energy

Question 19

Electromotive force (emf)

Answer 19

The potential difference between the anode and cathode in a cell

Also called cell potential Ecell

Question 20

Cell potential

Answer 20

Measured in volts = J/C

Question 21

The reduction potential for hydrogen

Answer 21

0 V

Question 22

Cell potential at standard conditions can be found with this eqn

Answer 22

Ecell = Ered (cathode) - Ered (anode)

Question 23

Relationship between oxidizers/reducers and reduction potential

Answer 23

The strongest oxidizers have the most positive reduction potentials

The strongest reducers have the most negative reduction potentials

Question 24

The greater the difference between the reduction potentials

Answer 24

The greater the voltage of the cell

Question 25

Free energy for a redox reaction

Answer 25

Delta G = -nFE
N is moles of electrons transferred
F is 96485 C/mol

Also applies under standard condition if E is standard

Question 26

Nernst equation

Answer 26

-nFE = -nFEstandard + RTlnQ

Question 27

Nernst equation at room temperature

Answer 27

E = Estandard - 0.0592/n logQ

Question 28

As long as the concentrations are different

Answer 28

E will not be 0