Redox

Question 1

Group 1 oxidation states

Answer 1

Always +1

Question 2

Group 2 oxidation states

Answer 2

Always +2

Question 3

Aluminum oxidation state

Answer 3

Always +3

Question 4

Fluorine oxidation state

Answer 4

Always -1

Question 5

Hydrogen oxidation states

Answer 5

Usually +1, except when with metals where it is -1

Question 6

Oxygen oxidation states

Answer 6

Usually -2, except with Fluorine where it is +2 or with a peroxide (O2) where it is -1

Question 7

What does the sum of the elements of a polyatomic ion must equal?

Answer 7

The overall charge of the polyatomic ion

Question 8

What is the sum of the atoms in a neutral compound?

Answer 8

= 0

Question 9

What is the oxidation state of an element when it is alone?

Answer 9

= 0

Question 10

Oxidation

Answer 10

lose electrons (LEO)
-addition of oxygen
-removal of hydrogen
-increase in oxidation state

Question 11

Reduction

Answer 11

gain electrons (GER)
-addition of hydrogen
-decrease in oxidation state
removal of oxygen

Question 12

What is the oxidation state when molecules contain more than one atom of an element?

Answer 12

The oxidation state is an average and can be an integer

Question 13

Steps of balancing an acidic redox rxn

Answer 13

1. Balance oxygen by adding H2O
2. Balance hydrogen by adding H+
3. Balance charge by adding electrons

Question 14

Steps of balancing a basic redox rxn

Answer 14

1. Balance oxygen by adding H2O
2. Balance hydrogen by adding H+
3. Balance charge by adding electrons
4. Add as many OH- as you have H+ to both sides

Question 15

Voltaic Cell

Answer 15

Spontaneous redox reaction
Chemical rxn that produces electrical energy
Two half cells connected by salt bridge

Question 16

Salt bridge

Answer 16

U-shaped tube with a saturated solution of NaNO3 or KNO3, allows ions to travel freely to maintain neutral solutions

Question 17

Anode (Voltaic)

Answer 17

Negative electrode where oxidation takes place

Question 18

Cathode (Voltaic)

Answer 18

Positive electrode where reduction takes place

Question 19

Standard conditions

Answer 19

1 mol/dm3 solutions
298K
100kPa for all gases
page 5 of data booklet

Question 20

Standard Hydrogen Electrode

Answer 20

Hydrogen is assigned a value of zero, all other values measured up or down from that

Question 21

What is used when a half cell does not contain metal?

Answer 21

Pt because it is inert and will not ionize

Question 22

(-) standard Hydrogen potential

Answer 22

non-spontaneous rxn

Question 23

+ standard hydrogen potential

Answer 23

spontaneous rxn

Question 24

Never multiply voltages by …

Answer 24

COEFFICIENTS

Question 25

Delta G + E° equation

Answer 25

Delta G = -nFE° n = # of moles exchanged F = Faraday's constant/96,500 coulombs *pg 2 data booklet*

Question 26

Delta G = +

Answer 26

nonspontaneous

Question 27

Delta G = -

Answer 27

spontaneous

Question 28

E° = +

Answer 28

spontaneous

Question 29

E° = -

Answer 29

nonspontaneous

Question 30

Electrolytic Cell

Answer 30

Nonspontaneous redox reaction Uses external power supply (battery) to cause a chemical reaction E° = negative One container, no salt bridge Inert electrodes (graphite or Pt)

Question 31

Anode (Electrolytic)

Answer 31

Positive electrode where oxidation takes place

Question 32

Cathode (Electrolytic)

Answer 32

Negative anode where reduction takes place

Question 33

Discharge

Answer 33

Got rid of charge

Question 34

Electrolysis of aqueous solutions

Answer 34

Contain water Water can be both oxidized and reduced Pure water is not a conductor, for the electrolysis of water NaOH is added

Question 35

Uses of electroplating

Answer 35

1. Decorative - gold plating or silver plating 2. Protective coating - Cooling Fe with Zinc 3. Improve function

Question 36

Electroplating

Answer 36

Coating a metal object with a thin coat of metal Object being electroplated is the cathode Solution contains metal ions which are to coat the object

Question 37

Current equation

Answer 37

I = q/t I = current q = charge (coulombs) t = time (sec)

Question 38

Steps for finding mass using current and time

Answer 38

1. Convert time to seconds 2. Plug into I=q/t 3. Take coulombs and multiply by 1 mole electrons/96500c 4. Multiply by moles of the element/moles of electrons 5. Multiply by molar mass of element/moles for the element

Question 39

Steps for finding coulombs using time and mass

Answer 39

1. Multiply mass by 1 mole of element/molar mass of element 2. Multiply by moles of electrons/moles of element 3. multiply by 96500c/1 mole of electrons

Question 40

Reducing Agent

Answer 40

Donates electrons - is oxidized

Question 41

Oxidizing Agent

Answer 41

Accepts electrons - is reduced