deck Flashcards

Question

how do you know which electrode in a voltaic cell is the anode vs cathode and which way do electrons flow

Answer 1

oxidation occurs at the anode (both vowels) (negative electrode) reduction occurs at the cathode (consanants) (positive electrode) since oxidation is losing electrons and reduction is gaining, the electrons flow from the anode to the cathode (alphabetically)

Answer 2

anions migrate towards the anode cathodes migrate towards the cathode since the anodes and cathodes generally submerged in their ion in aqueous form and that ion is a metal so its positive, those ions tend to flow through the boundary to the cathode. the cations flow this way to balance the charge of the whole cell because the electrons are also flowing to the cathode, so to keep it balanced the metal anion dissociates over time into its ions and the opposite happens at the cathode simultaneously to balance the charge, resulting in LOSS OF MASS at the ANION and GAIN OF MASS at the CATION

Answer 3

in acidic cells because NO3-(aq) + H+(aq) is a SOA (found at .80V on table)

Answer 4

in cells with silver or lead ions because it will form a precipitate

Answer 5

in cells with silver or lead ions because it will form a precipitate

Answer 6

E°net = E°rpc - E°rpa (1 value - another value, no multiplying) reduction potential at the CATHODE - reduction potential at the ANODE = electric potential difference

Answer 7

- mass gain at cathode (if its a metal) - loss of mass at anode (if its a metal) - pH change (increase of H+ in products, decrease if in reactants) - colour change of aqueous solution (production or consumption of a coloured ion, refer to page 11 data book)

Answer 8

just the umbrella term for voltaic and electrolytic cells

Answer 9

a non spontaneous reaction converting electrical energy to chemical Ep (reverse process of a voltaic cell require a current to be added chemical change THROUGH the application of electrical energy used to purify metals

Answer 10

voltaic voltaic electrolytic

Answer 11

electrolytic voltaic electrolytic

Answer 12

both voltaic electrolyitc

Answer 13

electrolytic electrolytic both

Answer 14

splitting water into H2(g) and O2(g), which are visible as bubbles (red. at cathode) the production of H2 also produces OH- so this area is basic (oxid. at anode) the production of O2 also produces H+ so this area is acidic water MUST be both the SOA and the SRA, meaning it will not happen correctly if there is a stronger OA or RA than water (there aren't many reactions on the table weaker than water so be careful...) added electrolyte to allow electron flow E°net = E°rc - E°ra = (-.80V) - (+1.23V) = -2.06V (reduction of water) - (oxidation of water)

Answer 15

(oxid. at anode) chloride ions form Cl2(g) (red. at cathode) sodium ions form Na(l) a major source of chlorine gas needs to be an electrolytic cell because otherwise once separated the Cl2(g) and the Na(l) would form NaCl again same E° applies, but when writing formulas we must write the altered states, and consider that there is no water present (can't be aqueous anyway) E°net = E°rc - E°ra = (-2.71V) - (+1.36V) = -4.07V (reduction of sodium) - (oxidation of chlorine)

Answer 16

very common, produces Cl2(g) for plastics/agriculture, H2(g) for fuel, and NaOH for industrial cleaners. produced simultaneously (oxid. at anode) chlorine gas produced at anode, THIS IS AN EXCEPTION, water "should" be oxidized here. (the Ea for chlorine in this one case is less than the Ea for water, you don't need to know that though) (red. at cathode) water is reduced to form hydrogen gas, also produces OH- which reacts with sodium ions to produce NaOH. sodium is not reduced here because water is SOA

Answer 17

- a metal ion is reduced to its solid metal form - the cathode is the object getting plated (because the metal cations flow to it and gain the e-, becoming the solid metal) and e-s are entering into the cathode, REDUCTION - anode is usually what is doing the plating but can also be inert - performed in an electrolyte (solution) of the metal ions that are to be plating the cathode - protects from corrosion, makes things look nice - plating with chromium is special and is more resistant to oxidation from environment than other metals *note - even when a reaction is not shown in the data book, you can infer it by adding the same amount of e- as the charge of the ion

Answer 18

- the breakdown of metals via e- transfer which is caused by exposure to O2(g) (it's like dissolving but metals) - rust is Fe(OH)2(s) in chem 30 (but there are further steps) - only a problem in iron because metal oxide is impermeable to O2(g) and H2O(l), the oxide layer usually stops oxidation because only the outermost layer oxidizes - all iron will continue to rust in the presence of ANY iron oxide

Answer 19

1. providing a barrier via painting, oiling, dipping, electroplating, alloying 2. sacrificial anode (providing alternative e- source) by adding another metal that is a SRA than Fe(s), however the alternative metal needs to be replaced every so often once it runs out of e- 3. impressed current (providing alternative e- source) where a current is sent through the object to provide e- and the Fe(s) will never lose its e- to oxidation because the O2 / H2O take e- from the Fe but the current instantly replaces it

Answer 20

Faraday's Law (allows to solve for moles but using n=m/M we can find mass)

Answer 21

A*s as in amperes x seconds

Answer 22

(A)(s)/n ampere x second / mole