EGEE 441: Electrochemistry L2 – Flashcards
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| what are the components of a typical electrochemical cell? |
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| electrodes electrolyte outer circuit |
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| an electrolytic cell... |
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| uses electricity to split a chemical compound |
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| the reduction reaction always tales place at the __ |
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| cathode |
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| the oxidation reaction always takes place at the __ |
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| anode |
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| mnemonic for remembering where half reactions take place |
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| A C OILRIG |
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| a galvanic cell... |
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| combines a chemical compound and produces electricity |
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| for an electrolytic cell, tell which electrode is positive and which is negative |
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| cathode: - anode: + |
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| for a galvanic cell, tell which electrode is positive and which is negative |
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| cathode: + anode: - |
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| between electrolytic cells and galvanic cells, the cathode-anode polarity is the same or reversed? |
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| reversed |
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| Faraday's law of electrolysis states... |
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| that the amount of substance produced/consumed in an electrochemical cell is proportional to the charge passed through the cell |
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| what is the physical meaning of Faraday's constant? |
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| tells the amount of electric charge carried by 1 mol of charged species |
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| is the electrical resistivity of pure water low or high? why? |
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| very high because of the low concentration of ions in pure water |
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| what is the volume of H2 produced vs. the volume of O2 produced in an electrolyzer? why? |
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| twice as much H2 is produced as O2 because there is twice as much H than O in water |
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| why is a strong base usually added to the solution of pure water for water electrolysis? |
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| to decrease the resistivity of pure water also, a strong base is less corrosive to the equipment than a strong acid |
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| the amount of charge passed through an electrolyzer can be found by... |
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| measuring the amount of gas produced |
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| what is Ohm's law? |
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| V = IR |
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| name Kirchhoff's 2 laws |
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| 1. the sum of the currents into a node equals the sum of the currents out of a node 2. the sum of voltage around a closed loop is zero |
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| what is the purpose of the salt bridge in the Daniell cell? |
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| to allow the flow of electrons between the electrodes while keeping the electrolyte solutions separate |
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| what is the sign of the potential difference between the cathode and anode for a galvanic cell, EGC? |
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| + |
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| is the potential difference between the cathode and anode for a galvanic cell, EGC, greater than or less than E at equilibrium? |
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| always less than Eeq |
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| what contributes to the internal resistance? |
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| R of the two electrolyte solutions R of the salt bridge R of the interfaces between the metal electrodes |
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| what is the sign of the potential difference between the cathode and anode for an electrolytic cell, EEC? |
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| + |
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| is the potential difference between the cathode and anode for an electrolytic cell, EEC, greater than or less than E at equilibrium? |
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| always greater than Eeq |
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| define decomposition potential, ED |
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| minimum theoretical potential at which electrolysis takes place |
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| how is the decomposition potential, ED, related to the equilibrium potential, Eeq? |
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| ED = -Eeq |
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| is the equilibrium potential positive or negative for a galvanic cell? |
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| + |
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| is the equilibrium potential positive or negative for an electrolytic cell? |
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| - |
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| what is the sign convention for equilibrium potential with respect to a spontaneous process? |
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| spontaneous: + nonspontaneous: - (opposite of ?G) |
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| between electrolytic mode and galvanic mode for the Daniell cell, is the polarity of cathode and anode the same or reversed? |
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| the same, but they switch sides so that: Cu electrode is always + Zn electrode is always - |
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| is it appropriate to use the terms "cathode" and "anode" for a Daniell cell? |
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| no use "+ electrode" and "- electrode" instead |
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| an equilibrium cell is a cell where... |
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| electricity is neither consumed nor produced |
