Unit 4: Electrochemistry Flashcards
How is the gain or loss of oxygen in a chemical reaction linked to oxidation and reduction?
Oxygen is not required, but it has to do with the loss and gain of electrons, like oxygen does.
How is the gain or loss of electrons in a chemical reaction linked to oxidation and reduction?
LEO: oxidation is the loss of electrons
GER: reduction is the gain of electrons
What happens to iron when it corrodes?
It becomes Iron (III) oxide (rust) through oxidation.
Determine the oxidation number of an atom of any element in a pure substance.
always 0 (zero)
Define oxidation and reduction in terms of a change in oxidation number and identify atoms being oxidized or reduced in redox reactions.
oxidation number increase = oxidation
oxidation number decrease = reduction
Use oxidation-number changes to balance redox equations
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Use half-reactions to balance redox equations.
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How do we determine what types of redox reactions are best balanced through the half-reaction method?
ionic reactions are best balanced through half-reaction
What happens to the voltage of the solution during the KMnO4 and FeCl2 titration?
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What is the balanced net ionic equation for the reaction of KMnO4 and FeCl2?
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What happens to the color of the FeCl2 when the equivalence point is reached?
.
For any two metals in an activity series, which metal is more readily oxidized?
the more active metal is oxidized (Li is most)
Who created the first electrochemical cell?
Volta
How does a voltaic cell produce electrical energy?
by spontaneous redox reactions
What occurs in a half-cell?
oxidation or reduction
What is the purpose of a salt bridge
allows ions to pass from one half-cell to the other
What is the electrolyte in a dry cell?
paste - MnO2, ZnCl2, NH4Cl, H2O, and graphite powder
What is the electrolyte in a lead storage battery?
Sulfuric Acid (H2SO4 (aq))
How is a lead battery recharged? Why can’t a lead storage battery be recharged indefinitely?
Through the reverse reaction
Due to the loss of lead sulfate to the bottom of the cells
How do fuel cells work?
voltaic cells in which a fuel substance undergoes ox & red; from which electrical energy is continuously obtained
How does hydrogen-oxygen fuel cell work? What are the products of hydrogen-oxygen fuel cells?
The combination of H and O2 to make water (H2O)
What is needed for a redox reaction to be used as a source of electrical energy?
the two half reactions must be physically separated
Which electrode (anode or cathode) is positive in an electrolytic cell? In a voltaic cell? What is the direction of electron flow in an electrolytic cell? In a voltaic cell? Where does ox & red occur in these cells?
electrolytic - anode +, cathode -; anode (ox) to cathode (red)
voltaic - anode -, cathode +; anode (ox) to cathode (red)
What electrolyte can be used to electrolyze water?
H2SO4, KNO3; any electrolyte (aq) that is more easily ox or red than water
What gas is produce at the cathode in the electrolysis of brine?
hydrogen gas (H2 (g)) is produced at the cathode in the electrolysis of brine
What is electroplating? In electroplating, where is the object to be electroplating is placed?
the use of an electrolytic cell to deposit a thin layer of metal on an object
the object being electroplated is placed as the cathode
