electrochemistry Flashcards
what is reduction? (2 definitions-electron side?)
- ore to metal
GAIN of electrons that cause DECEASE in charge (oxidation numbers) - electrons on left side
what is oxidation? (2 definitions- electron side?)
-reaction with oxygen
- LOSS of electrons cause INCREASE in charge & BREAKDOWN material
- electrons on right side
what’s a redox/electrochemical reaction? how do you balance?
- involves transfer of electrons
- reduction & oxidation reaction
-break into half reactions to balance
what makes it a complex 1/2 reaction?
- involves polyatomic ions & compounds in acidic & basic conditions
how to balance acidic conditions? (PH<7)
1 balance principle atoms
2 balance O with H2O
3 balance H with H+
4 balance charge with electron
5 reduction or oxidation
how to balance basic conditions? (PH >7)
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
what’s an OA?
- oxidizing agents are attractive to electrons= recives electrons
- highly electronegative
-gets reduced - cations, halogens, acids
what’s an RA?
- reducing agents are not attractive to electrons=gives electron away
-Poor electronegativity
-gets oxidized
-anions, metals, bases
what makes it spontaneous?
for something to happen, the OA must be above the RA
what makes it non spontaneous?
nothing happens when the OA is below the RA
what’s a predominant reaction?
reaction between the strongest OA, and the strongest RA
what is amphoteric?
A chemical that is both an OA and RA
- usually multivalent(transition metals)
what are the steps for redox stoichiometry?
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)
oxidation numbers?
- calculated to keep track of electron gain or loss
-Some of oxidation numbers will always equal overall charge
what’s a redox titration?
-evaluates concentration
-Titrate(known concentration) (top)
-analant(unknown concentration) (bottom)
- 3 trials=eliminate one & find adverage of others
where do you apply redox reactions?
(1) a,b 2)
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)
what is electrolysis?
-use of electricity to break things down
-Used for non-spontaneous
-Find potential difference (OA -RA)
what is a voltaic cell?
LEOA the lion says GERC
- 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
what does the cell notation look like for a voltaic cell?
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)
what’s an inert electrode?
C and Pt unreactive which allow electron transfer(not included in cell notation)
when is a battery dead? what will recharging it do?
-The anode breaks down entirely, and there is no more electrons to transfer
-recharging the battery forces products to become reactants(reverse reaction)
what is an electrolytic cell?
-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
what is the cell notation for electrolytic cells?
anode (-)|electrolyte|cathode (+)
measuring volts & current:
- 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
mass change formula:
M(molar mass)I(current)n(moles)t(time)
/Fn(faraday’s number)e-(moles per electrons)
