E LECTROCHEMISTRY Kristin Shepard Brooke Petersen

E LECTROCHEMICAL C ELLS - T ERMS Electrode - Any cell that is used to conduct electricity; Where the reaction actually takes place- Solid Part Anode - Solid where the oxidizing happens Cathode - Solid where the reduction occurs Current - The flow of electrons- Electricity Salt Bridge - Concentrated salt solution with ions that will not react with solutions

S TANDARD C ELL P OTENTIAL Standard Cell Potential is known as E° There are four simple steps 1. Even the electrons 2. Flip the most negative equation 3. Add the equations 4. Add the E°

C ALCULATING ∆G° To calculate this, we use the following equation when all substances are at standard conditions ∆G°= -nFE°

C ALCULATING K After finding the ∆G°, we can now find K using: ∆G°= -RTlnK

H OW MANY MOLS OF P T MAY BE DEPOSITED ON THE CATHODE WHEN 0.80 F OF ELECTRICITY IS PASSED THROUGH A 1.0 M SOLUTION OF PT 4+ ? (A) 1.0 mol (B) 0.60 mol (C) 0.20 mol (D) 0.80 mol (E) 0.40 mol It takes 4 mol of electrons (4F) to change the platinum ions to platinum metal. The calculation would be: (0.80)(1 mol Pt/4 F)= 0.20 mol Pt.

W HAT HAPPENS TO THE CELL VOLTAGE WHEN THE COPPER ELECTRODE IS MADE SMALLER ? (A) There is no change in the voltage. (B) The voltage becomes zero. (C) The voltage increases. (D) The voltage decreases, but stays positive. (E) The voltage becomes negative. The size of the electrode is not important.

W HAT HAPPENS TO THE CELL VOLTAGE AFTER THE CELL HAS OPERATED FOR 10 MINUTES ? (A) There is no change in the voltage. (B) The voltage becomes zero. (C) The voltage increases. (D) The voltage decreases, but stays positive. (E) The voltage becomes negative. As the cell operates, the copper ion concentration would decrease and the zinc ion concentration would increase. Both of these changes would make the logarithm term in the Nernst equation more negative. This would decrease the voltage.