Electrode Potentials and Fuel Cells

Question 1

Metal(s)/Metal Ion(aq)

Answer 1

• Metal ion in solution

* Metal electrode

Question 2

Non-metal(g)/Non-metal Ion(aq)

Answer 2

• Non-metal gas
• Platinum electrode
• Non-metal ion in solution

Question 3

Metal Ion(aq)/Metal Ion(aq)

Answer 3

• Platinum electrode

* Both metal ions in the same solution

Question 4

Why is platinum used as the electrode in half-cells?

Answer 4

• Platinum is unreactive

Question 5

Standard hydrogen electrode

Answer 5

• Platinum electrode (s)
• 100kPa/298K H₂ (g)
• 1.0 mol dm⁻³ H⁺ (aq)

Question 6

Even though a reaction may be thermodynamically feasible it may not occur because…

Answer 6

• Not carried out under standard conditions

* Activation energy is too high

Question 7

FCVs can be fuelled by…

Answer 7

• Hydrogen gas

* Hydrogen-rich fuels (methanol)

Question 8

How can we store Hydrogen in FCVs?

Answer 8

• as a liquid under pressure
• absorbed on the surface of a solid material
• absorbed within a solid material

Question 9

Advantages of FCVs

Answer 9

• Less pollution and less CO₂/only produces H₂O

* Greater Efficiency

Question 10

Disadvantages of FCVs

Answer 10

• Difficult to store and transport hydrogen fuel
• Limited lifetime
• Hydrogen is explosive

Question 11

REDOX

Answer 11

A reaction where both oxidation and reduction take place.

Question 12

OXIDATION NUMBER

Answer 12

The number of electrons that an atom uses to bond with atoms of a different element.

Question 13

OXIDISING AGENT

Answer 13

A reagent that oxidises (takes electrons from) another species.

Question 14

REDUCING AGENT

Answer 14

A reagent that reduces (adds electrons to) another species.

Question 15

STANDARD ELECTRODE POTENTIAL, Eθ

Answer 15

Is the e.m.f of a half cell compared with a standard hydrogen half cell, measured at 298K with all solution concentrations of 1 mol dm⁻³ and a gas pressure of 100kPa (1 atm)

Question 16

FUEL CELL

Answer 16

Uses the energy from the reaction of a fuel with oxygen to create a voltage.
½O₂ + H₂ → H₂O

Question 17

Charge carriers through the wire

Answer 17

Electrons

Question 18

Charge carriers through the solution and salt bridge

Answer 18

Ions

Question 19

What electrode does oxidation and reduction take place at?

Answer 19

Oxidation: negative
Reduction: positive

Question 20

State and explain how the cell voltage will change when [Cu2+] is increased, at the positive electrode.

Answer 20

• Equilibrium shifts to RHS
• Electrode potential increases
• Cell potential increases

Question 21

State and explain how the cell voltage will change when [Cu2+] is decreased, at the positive electrode.

Answer 21

• Equilibrium shifts to LHS
• Electrode potential increases
• Cell potential decreases

Question 22

State and explain how the cell voltage will change when [Cu2+] is increased, at the negative electrode

Answer 22

• Equilibrium shifts to RHS
• Electrode potential increases
• Cell potential decreases

Question 23

State and explain how the cell voltage will change when [Cu2+] is decreased, at the negative electrode

Answer 23

• Equilibrium shifts to LHS
• Electrode potential increases
• Cell potential increases