unit 11 - redox

Question 1

what are redox reactions caused by

Answer 1

caused by competition of atoms for electrons

Question 2

redox is an abbreviation for

Answer 2

Reduction/Oxidation Reactions

Question 3

oxidation

Answer 3

• The LOSS of electrons.
• Charge becomes more positive

Question 4

reduction

Answer 4

• The GAIN of electrons.
• Charge becomes more negative

Question 5

ATOMS are neutral but in a bond there is

Answer 5

shuffling of electrons (sharing, transferring) which ultimately gives them an “apparent” charge.

• this apparent charge is the Oxidation Number

Question 6

Oxidation Number

Answer 6

The ”apparent charge” on an atom in a compound, due to difference in electronegativity and bonding

Question 7

Ion

Answer 7

Charge an atom becomes when it gains or loses electron(s).

Question 8

Redox: Rule 1

Answer 8

all neutral compounds must sum to the total charge of ZERO

Question 9

Redox: Rule 2

Answer 9

polyatomic ions have a sum of charges equal to the ion’s charge

Question 10

Redox: Rule 3

Answer 10

Any atom uncombined has an oxidation of zero, because atoms are neutral

Question 11

Redox: Rule 4

Answer 11

Charge on a mono-atomic ion equals the charge of the ion

Question 12

Redox: Rule 5

Answer 12

In Binary Compounds the MORE electronegative element is assigned FIRST (it’s the oxidation number is the name charge as an ion)

Question 13

Redox: Rule 6

Answer 13

Elements in groups 1, 2, & aluminum have oxidation states ALWAYS +1, +2, and +3 respectively

Question 14

Redox: Rule 8

Answer 14

oxygen is always -2 unless its combined with fluorine (OF2), then its +2, or in a peroxide (H2O2) then its -1

Question 14

Redox: Rule 7

Answer 14

• Fluorine is the MOST ELECTRONEGATIVE ELEMENT so it takes precedence over ANY
• fluorine will always have a -1 oxidation #

Question 15

Redox: Rule 9

Answer 15

hydrogen is +1; unless it combines with a metal then its -1 because thats a hydride

Question 16

redox is a reaction defined by

Answer 16

the transfer of electrons

Question 17

LEO the Lion says GER

Answer 17

Lose Electrons Oxidize
Gain Electrons Reduction

Question 18

redox reaction can be broken into two parts that happen…

Answer 18

simultaneously!!
- oxidation and reduction

Question 19

what typa reaction is never redox?

Answer 19

double replacement

Question 20

hint to identify redox!!

Answer 20

• if theres a free guy and hes a compound on the otherside, yk it’s a redox

Question 21

oxidizing agent

Answer 21

The substance that makes
something else undergo oxidation.

• Takes away the electrons (it gains electrons)
• Oxidizing Agent is also Reduced

Question 22

reducing agent

Answer 22

Any substance that makes
something else gain electrons.

• Supplies Electrons (it loses electrons)
• Reducing Agent is also Oxidized

Question 23

what gets oxidized is the ____ agent

Answer 23

reducing agent

Question 24

what gets reduced is the ____ agent

Answer 24

oxidizing agent

Question 25

in redox reactions, electrons shift from

Answer 25

one atom/species to another SIMULTANEOUSLY!!

Question 26

half reaction

Answer 26

an equation which shows only a reduction OR oxidation

Question 27

half reactions show conservations of what? exceptions?

Answer 27

**show conservation of Mass, Charge, and Energy - except for Nuclear Reactions

Question 28

Redox reactions like all chemical reactions MUST be balanced to show conservation of

Answer 28

mass, charge, and energy

Question 29

shortcut for balancing redox

Answer 29

the difference in charge is the coefficient of the opposite - does not work if you have diatomics

Question 30

when a redox reaction takes place in an acidic solution,

Answer 30

it has excess H+ ion concentration as opposed to neutral conditions

Question 31

redox in acidic: what are we adding

Answer 31

We will now add Water molecules and H+ ions to balance the Oxygens & Hydrogens under acidic conditions.

Question 32

voltaic cells

Answer 32

- are electrochemical cells (batteries) - involve a spontaneous redox reaction - chemical energy is converted into electrical energy

Question 33

voltaic cells setup: two electrodes

Answer 33

are the site of oxidation/reduction

Question 34

voltaic cells setup: salt bridge

Answer 34

connects the two containers and produces the path for a flow of ions

Question 35

voltaic cells setup: the wires of voltmeter

Answer 35

connect the 2 half cells and electrons travel through them

Question 36

voltaic cell: table j

Answer 36

- most active metals lose electrons easily - top: atom oxidized - bottom: ion reduced

Question 37

voltaic cell: anode

Answer 37

Anode is the site of oxidation

Question 38

voltaic cell: cathode

Answer 38

cathode is site of reduction

Question 39

voltaic cell: electrons move from...

Answer 39

anode to cathode through the wire

Question 40

voltaic cell: anode mass/size

Answer 40

anode decreases in mass/size

Question 41

voltaic cell: cathode mass/size

Answer 41

cathode increases in mass/size

Question 42

voltaic cell: ions move through

Answer 42

Ions (+/-) move through salt bridge in the direction of electrode with same charge to maintain neutrality.

Question 43

voltaic cell: battery

Answer 43

battery will die and voltage will read zero (state of equilibrium)

Question 44

maximum battery voltage or cell potential

Answer 44

- based reduction potential chart * cell potential (v) = reduction potential (v) - oxidation potential (v)

Question 45

if cell potential (+)

Answer 45

reaction is spontaneous

Question 46

if cell potential (-)

Answer 46

reaction is nonspontaneous

Question 47

predicting spontaneous reactions

Answer 47

* one metal must be neutral ex. Mg (s) or Al (s) these can be oxidized (lose electrons) * the other must be an ion ex. Mg^+2 or Al^+3 these can be reduced (gain electrons)

Question 48

predicting spontaneous reactions: table j

Answer 48

the metal atom being oxidized (the neutral one) must be higher on the table J than the ion being reduced

Question 49

electrolysis

Answer 49

- is a non spontaneous reaction - requires electricity (battery)

Question 50

electrolytic cells:

Answer 50

- electrolysis - requires electricity - need an electric generator (battery) placed into the circuit to force electrons to flow from the anode (+) to the cathode (-) - electrical energy drives a chemical (redox rxn)

Question 51

electroplating

Answer 51

used to plate expensive metal on top of cheaper metals

Question 52

electrolytic: anode

Answer 52

● (+) ● always the expensive metal ● site of oxidation

Question 53

electrolytic: cathode

Answer 53

● (-) ● site of reduction

Question 54

electrolytic cells are used to

Answer 54

retrieve very active metals (group 1 & 2) from salts that contain them