13 Oxidation-Reduction and Electrochemistry

Question 1

The oxidation state of an atom that is not bonded to an atom of another element is

Answer 1

zero. That means either an atom that is not bonded to any other atom or an atom that is bonded to another atom of the same element.

Question 2

the oxidation numbers for all the atoms in a molecule must

Answer 2

add up to zero.

Question 3

The oxidation numbers for allt he atoms in a polyatomic ion must add up to

Answer 3

the charge of the ion.

Question 4

Oxidation Numbers:

Alkali Metals (Li, Na, . . .)

Answer 4

+1

Question 5

Oxidation Numbers

Alkaline Earths( Be, Mg, . . .)

Answer 5

+2

Question 6

Oxidation Numbers

Group 3A (B, Al, . . .)

Answer 6

+3

Question 7

Oxidation Numbers

Oxygen

Answer 7

-2

Question 8

Oxidation Numbers

Halogens (F, Cl, . . .)

Answer 8

-1

Question 9

Hydroxide

Answer 9

OH^-

Question 10

Nitrate

Answer 10

NO₃^-

Question 11

Perchlorate

Answer 11

ClO₄^-

Question 12

Acetate

Answer 12

C2H3O2^-

Question 13

Carbonate

Answer 13

CO₃^2-

Question 14

Sulfate

Answer 14

SO₄^2-

Question 15

Phosphate

Answer 15

PO₄^3-

Question 16

When an atom gains electrons, its oxidation number

Answer 16

decreases, and it is said too have been reduced.

Reduction is Gain

Question 17

When an atom loses electrons, its oxidation number

Answer 17

increases, and it is said to have been oxidized.

Oxidation is Loss

Question 18

If an atom is losing electrons and being oxidized, it must be giving the electrons to another atom, which is being reduced. So if a reactant contains an atom that is being oxidized,

Answer 18

it is a reducing agent or a deductant

Question 19

If an atom is taking electrons and being reduced, it must be taking electrons away from another atom, which is being oxidized. So if a reactant contains an atom that is being reduced, it is an

Answer 19

oxidizing agent or oxidant.

Question 20

{Delta}Gº =

Answer 20

-nFEº

{Delta}Gº = Standard Gibbs Free energy change (kJ/mol)

n = the number of moles of electrons exchanged in the reaction (mol)

F = Faraday’s constant, 96,500 coulombs (that is 1 mole of electrons has a charge of 96,500 coulombs)

E = Standard reaction potential (V)

Question 21

If Eº is positive, {Delta}Gº is

Answer 21

negative and the reaction is spontaneous, and if Eº is negative, {Delta}Gº is positive and the reaction is nonspontaneous.

Question 22

E =

Answer 22

(RT/nF)lnk

E = standard reduction potential

R = the gas constant, 8.31 (volt-coulomb)/ (mol-K)

T= absolute temperatuer (K)

n = the number of moles of electrons exchanged in the reaction (mol)

F = Faradyay’s constant, 96,500 coulombs/mole

K= equilibrium constant

Question 23

Oxidation takes place at the electrode called the

Answer 23

anode. Reduction takes place at the electrode called the cathode.

AN OX

RED CAT

Question 24

As the concentration of the products of a redox reaction increases, the voltage

Answer 24

decreases; and as the concentration of the reactants in a redox reaction increases, the voltage increases.

Question 25

In an Electrolytic cell, an outside source is used to force

Answer 25

a nonspontaneous reaction to take place.

Question 26

In a galvanic Cell a spontaneous

Answer 26

redox reaction is used to generate a flow of current

Question 27

I =

Answer 27

q / t

I = current (amperes)

q = charge (coulombs, C)

t = time (sec)

Question 28

Current is defined as the flow of

Answer 28

positive charge, so current is always in the opposite direction from the flow of electrons.

Question 29

In a galvanic cell,

Answer 29

a spontaneous redox reaction is used to generate current.

Question 30

At 25º C(298K), the Voltage Equilibrium equation simplifies too

log K =

Answer 30

nEº / 0.0592

Question 31

To calculate the potential of a redox reaction;

Add the potential for the oxidation half-reaction to

Answer 31

the potential for the reduction half reaction

Never multiply the potentiial for a half-reaction by a coefficient

Question 32

1 mole of e^- =

Answer 32

1 Faraday