Galvanic cells and equilibrium considerations

Question 1

As an example: Cu2+ + 2e- ⇌ Cu E0 = + 0,34 V

What happens if the concentration of Cu2+ ions increases?

Answer 1

If the concentration of the Cu2+ solution is increased, according to LCP, the reduction of Cu2+ will be favoured.
o Relative to a standard hydrogen electrode, the Cu 1⁄2 cell would now be even more positive, and so the Ecell value would become more positive.

Question 2

As an example: Cu2+ + 2e- ⇌ Cu E0 = + 0,34 V

What happens if the concentration of Cu2+ ions decreases?

Answer 2

A decrease in the concentration of Cu2+ would, conversely, favour the oxidation of Cu and make the Ecell value less positive.

Question 3

With time, this 1⁄2 cell will reach an equilibrium, and no further (net) reduction or oxidation will take place. The E0 value tends to ___. (this is true of all 1⁄2 cells and is why batteries will eventually stop working).

Answer 3

zero

Question 4

In galvanic cells, any changes to the 1⁄2 cells (in terms of concentration, pressure and temperature) will affect the ___ of the galvanic cell.

Answer 4

EMF

Question 5

As a rule of thumb: (2)

Answer 5

o Changes that favour oxidation at the anode and reduction at the cathode INCREASE the EMF of the cell
o Changes that favour reduction at the anode and oxidation at the cathode DECREASE the EMF of the cell

Question 6

What are factors that affect EMF?

Answer 6

Factors that can affect the EMF of a

galvanic cell are those factors which change the likelihood of reduction or oxidation of the species in the 1⁄2 cells.

Question 7

Changing factors that increase the ___ of electron transfer or ion movement do not change the EMF but can change the efficiency of the cell and the amount of
current it can deliver. For example: (2)

Answer 7

o Increasing electrode surface area – increases the rate of oxidation or reduction and so would increase current delivery by the cell, but the EMF would not change.

o Increasing the size of the salt bridge – increases the ease with which ions transfer between 1⁄2 cells and effectively lowers the internal resistance of the cell. Again, current deliver would increase, but there would be no affect on EMF. (shorter salt bridge)

Question 8

If V is connected there will be no ____. No ____ will be restablished as oxidation and reduction are not taking place.

Answer 8

current