electrochemistry

Question 1

what is reduction? (2 definitions-electron side?)

Answer 1

• ore to metal
  GAIN of electrons that cause DECEASE in charge (oxidation numbers)
• electrons on left side

Question 2

what is oxidation? (2 definitions- electron side?)

Answer 2

-reaction with oxygen
- LOSS of electrons cause INCREASE in charge & BREAKDOWN material
- electrons on right side

Question 3

what’s a redox/electrochemical reaction? how do you balance?

Answer 3

• involves transfer of electrons
• reduction & oxidation reaction
  -break into half reactions to balance

Question 4

what makes it a complex 1/2 reaction?

Answer 4

• involves polyatomic ions & compounds in acidic & basic conditions

Question 5

how to balance acidic conditions? (PH<7)

Answer 5

1 balance principle atoms
2 balance O with H2O
3 balance H with H+
4 balance charge with electron
5 reduction or oxidation

Question 6

how to balance basic conditions? (PH >7)

Answer 6

1 balance principle atoms
2 balance O with H2O
3 balance H with H+
4 neutralize H with OH
5 make H2O
6 eliminate spectators
7 balance charge with electron
8 reduction or oxidation

Question 7

what’s an OA?

Answer 7

• oxidizing agents are attractive to electrons= recives electrons
• highly electronegative
  -gets reduced
• cations, halogens, acids

Question 8

what’s an RA?

Answer 8

• reducing agents are not attractive to electrons=gives electron away
  -Poor electronegativity
  -gets oxidized
  -anions, metals, bases

Question 9

what makes it spontaneous?

Answer 9

for something to happen, the OA must be above the RA

Question 10

what makes it non spontaneous?

Answer 10

nothing happens when the OA is below the RA

Question 11

what’s a predominant reaction?

Answer 11

reaction between the strongest OA, and the strongest RA

Question 12

what is amphoteric?

Answer 12

A chemical that is both an OA and RA
- usually multivalent(transition metals)

Question 13

what are the steps for redox stoichiometry?

Answer 13

1 write balanced redox reaction (1/2 rxn-> combine)
2 find number of moles (m/M= CV)
3 apply mole-mole ratio (want/have)
4 find desired quantity (m, C=n/V, V=n/C)

Question 14

oxidation numbers?

Answer 14

• calculated to keep track of electron gain or loss
  -Some of oxidation numbers will always equal overall charge

Question 15

what’s a redox titration?

Answer 15

-evaluates concentration
-Titrate(known concentration) (top)
-analant(unknown concentration) (bottom)
- 3 trials=eliminate one & find adverage of others

Question 16

where do you apply redox reactions?
(1) a,b 2)

Answer 16

1) to protect from corrosion
a. impressed current= applying electrical current to replace lost electron(expensive)
b. Sacrificial anode= stronger RA, consumed first, continual replacement required.
2) electrochemical cells
a. Packages of chemicals, that react and transfer electrons(battery-Alessandro Volta)

Question 17

what is electrolysis?

Answer 17

-use of electricity to break things down
-Used for non-spontaneous
-Find potential difference (OA -RA)

Question 18

what is a voltaic cell?
LEOA the lion says GERC

Answer 18

• Package of chemicals that react spontaneously and generate voltage
• 1 V=1 J/C (charge)
  -battery’s left side=SOA, cathode, reduction, attractive to e-) (GERC)
• battery’s right side= SRA, anode, oxidation, give e away

Question 19

what does the cell notation look like for a voltaic cell?

Answer 19

anode|electrolyte||electrolyte|cathode
- includes pours boundary, salt bridge, & external electron circuit
anode-SRA (becomes more + b/c it gives e away)
cathode-SOA (becomes more - b/c it receives e)

Question 20

what’s an inert electrode?

Answer 20

C and Pt unreactive which allow electron transfer(not included in cell notation)

Question 21

when is a battery dead? what will recharging it do?

Answer 21

-The anode breaks down entirely, and there is no more electrons to transfer
-recharging the battery forces products to become reactants(reverse reaction)

Question 22

what is an electrolytic cell?

Answer 22

-Packages of chemicals that react non-spontaneously and require voltage
- anode = +, gives electrons away
-cathode= -, receives electrons
-a. Electro refining- ore to metal
b. electroplating

Question 23

what is the cell notation for electrolytic cells?

Answer 23

anode (-)|electrolyte|cathode (+)

Question 24

measuring volts & current:

Answer 24

• 1 V= 1 J/C coulomb
  -use unit analysis
  -measures energy carried by charged particles
• current measure of how much charge is being moved(A)
• current is inversely proportional to how long a battery lasts
• Bigger batteries last longer b/c SRA and transfers electrons for longer

Question 25

mass change formula:

Answer 25

M(molar mass)I(current)n(moles)t(time)
/Fn(faraday’s number)e-(moles per electrons)