Cell potentials 186-187

Question 1

Define the term, standard electrode potential.

Answer 1

The standard electrode potential of a half cell, E, is the e.m.f of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 mol dm^-3 and a gas pressure of 100KPa.

Question 2

What is the standard electrode potental of a hydrogen half cell?

Answer 2

0 V

Question 3

How do you measure the standard electrode potentials?

Answer 3

A standard electrode potential is measured by conecting a standard half cell to a standard hydrogen half cell. The reading on the voltmeter gives the standard electrode potential of the zinc half cell.

Question 4

A silver-copper cell is made by connecting together two half cells:

An Ag/Ag+ half cell E= +0.80V

An Cu/Cu2+ half cell E = +0.34V

Find out which electrode has the positive terminal and which has the negative terminal.

Calculate the standard cell potential of this setup.

Answer 4

• Ag/Ag+ is more positive so it has the positive end of the terminal.
• E_cell =E(positive terminal) - E(negative terminal)

+0.80-(+0.34) = 0.46V