Developing Metals 4: Standard Electrode Potentials

Question 1

Definition of standard electrode potential of a half-cell

Answer 1

Voltage of a half cell compared with a standard hydrogen electrode

( think about heights compared to wooden post analogy )

Question 2

Describe what is contained in a standard hydrogen electrode

Answer 2

• platinum ( submerged in )
• 1 moldm-3 of H+ ions
• H2 gas bubbled through
• at 10^5 Pa pressure & 298K temp

Question 3

Describe what happens in a standard hydrogen electrode

Answer 3

• platinum electrode surface absorbs hydrogen gas and an equilibrium is set up

Question 4

Give the equilibrium equation for reaction that take place in standard hydrogen electrode

Answer 4

2H+ (aq) + 2e- <=> H2 ( g )

written in direction of reduction

Question 5

Be able to draw labeled diagram of standard hydrogen electrode

Answer 5

Look in notes

Make sure give conditions required and temperatures

Question 6

What is the electrode potential of the hydrogen half cell

And what is used for

Answer 6

Electrode potential = 0

• known as reference cell
• all other standard electrode potentials are measured against it

Question 7

What is the setup like when measuring standard electrode potentials against the standard hydrogen electrode

Answer 7

• hydrogen electrode always on left

Question 8

What does E represent

Answer 8

E= voltage

= standard electrode potential for half a cell

Question 9

What the equation for whole cell potential in terms of E

Answer 9

Whole cell potential
=E (RHS) - E (LHS)

= E ( most +ve) - E ( most -ve )

Question 10

What do -ve and +ve represent

Answer 10

Which way the electrons flow

Question 11

What is the charge of the whole cell potential ( E cell ) always going to be and why

Answer 11

+ve

• more -ve value is being subtracted from more +ve value

Question 12

Describe a potential difference chart ( electrode potential chart ) and its rules

Answer 12

1. Write more -ve electrode potential first ( oxidised substance )
2. Top reaction goes backwards
   Bottom reaction goes forward = anti-clockwise rule

Question 13

Be able to draw potential difference chart for a zinc/ copper cell and calculate E cell value

Zinc = -0.76 V
Copper = +0.34 V

Answer 13

Look in notes.

• zinc equation goes at top

Question 14

What is the anti-clockwise rule ( for a potential difference chart )

Answer 14

Top reaction goes backwards and bottom reaction goes forward