Topic 11: REDOX Reactions and Batteries

Question 1

How is electricity produced?

Answer 1

By moving electrons from one atom to another

Question 2

Anode

Answer 2

One half of the battery which electrons come out of (OXIDATION)

Question 3

Cathode

Answer 3

One half of the battery which electrons return to (REDUCTION)

Question 4

Oxidation

Answer 4

The process of losing electrons
Occurs at the anode

Question 5

Reduction

Answer 5

The process of gaining electrons
Occurs at the cathode

Question 6

Oxidation half reactions
-What happens to the charge?
-What are the products and reactants?

Answer 6

-oxidation number will always go up
-Electrons are written on the product side along with the element’s new charge

Question 7

Reduction half reactions
-What happens to the charge?
-What are the products and reactants?

Answer 7

-oxidation number will always go down
-electrons and element are always on reactant side

Question 8

REDOX

Answer 8

combined REDuction-OXidation reactions:

-number of electrons lost= number gained
-sum of all charges = 0
-do not include electrons

Question 9

How to balance a REDOX reaction

Answer 9

multiply half reactions so they will lose and gain the same amount of electrons

Question 10

How to assign oxidation states (charges)

Answer 10

1. elements not bonded always = 0
2. if bonded, oxidation state is (usually) the highest one on PT
3. sum of all charges will = 0

Question 11

how do you know which element is losing/gaining electrons in a combined REDOX reaction?

Answer 11

Oxidation/losing: charge always goes UP
Reduction/gaining: charge always goes DOWN

Question 12

How do you determine if a reaction is spontaneous?

Answer 12

The most reactive metal will oxidize, the most reactive non-metal will reduce.

Question 13

How do you determine if a reaction is NOT spontaneous?

Answer 13

The most reactive metal will reduce,
the most reactive non-metal will oxidize.

Question 14

Table J: spontaneous oxidation and reduction nonmetals vs. metals

Answer 14

METAL: will spontaneously lose electrons to another metal BELOW it (O)

NONMETAL: will spontaneously TAKE electrons from another nonmental BELOW it (R)

Question 15

Voltaic cells
-what do they convert
-parts of
-determining anode and cathode
-changes in mass
-Spontaneous or not

Answer 15

-Chemical energy to Electrical energy
-spontaneous
-Batteries with anode and cathode
-have a salt bridge (promoting ION exchange and maintains electrical neutrality in A and C)
-anode= higher on Table J (more active) and will LOSE mass
-cathode= lower on Table J (less active) and will GAIN mass

Question 16

Electrolytic cells
-what do they convert
-spontaneous or not

Answer 16

-(use) Electrical energy (convert) to Chemical energy
-not spontaneous
-processes= electroplating and electrolysis

Question 17

What is electroplating?

Answer 17

1. piece of metal is plated
2. piece is attached to the NEG anode of a battery and the POS cathode

NEG charge allows the piece to attract positive metal ions
POS charge allows the piece to lose electrons and dissolve

Question 18

What is electrolysis?

Answer 18

1. Water molecules can be split using a battery

Hydrogen (POS) is attracted to NEG end of battery
Oxygen (NEG) is attracted to positive end of battery