Chemistry · Chapter 17

Nernst and the Dying Battery

Slide the ion concentrations and the cell potential walks along a straight line. Then discharge the cell for real and trace the voltage all the way down to zero, which is the moment Q finally catches up with K.

Your spot on the Nernst line slope is −0.0592/n

Cell potential against log Q, with the point where the cell dies

Discharge trace one litre in each half-cell

Voltage falling as charge leaves the cell

Choose a cell

Set the concentrations

1.00 M
1.00 M

The meter

1.10volts healthy
Standard value: 1.10 V
Reaction quotient: 1.00
log Q: 0.00
Nernst correction: −0.000 V
Dead when log Q reaches: 37.16
Charge already drawn: 0.00 mol of electrons
Standard conditions
Fresh and full
Both ions sit at 1 M, so Q is 1 and log Q is 0. The meter reads the standard value exactly.