Electrochemistry

Question 1

How do you solve electrochemical equations?

Answer 1

Reverse one of the reactions
Multiply so the number of electrons are the same
Combine the equations
Cancel anything out
Voltage should be positive

Question 2

How do hydrogen fuel cells work?

Answer 2

Uses energy from the reaction of a fuel with oxygen to create a voltage

Question 3

What is the reaction in hydrogen fuel cells?

Answer 3

2H2 (g) + O2 (g) –> 2H2O (l)
+1.23 V

Question 4

What are the advantages of hydrogen fuel cells?

Answer 4

• non-polluting, only product is water
• more efficient, no energy lost
• continuous process

Question 5

What are the disadvantages of hydrogen fuel cells?

Answer 5

• perceived as explosive
• gas - liquefy -252.9oC
• costly process to store at such low temperatures

Question 6

What are ‘Hydrogen-rich’ fuel cells?

Answer 6

direct-methanol fuel cells (DMFCs)

Question 7

What is the equation for ‘Hydrogen-rich’ fuel cells?

Answer 7

CH40 (l) _ 1.5O2 (g) –> CO2 (g) + 2H2O (l)

Question 8

What are the advantages of ‘Hydrogen-rich’ fuel cells?

Answer 8

• liquids, easy to store
• no need to liquiefy
• alcohol from plants (fermentation of glucose) (CO2 neutral)

Question 9

What are the disadvantages of ‘Hydrogen-rich’ fuel cells?

Answer 9

• produces CO2

Question 10

What is the definition of Standard Electrode Potentials?

Answer 10

voltage created by half cell when connected to standard hydrogen electrode at 25oC, 1 atm pressure and with 1 moldm-3 solutions of ions

Question 11

What are the three types of half cells and their equations?

Answer 11

Metal based (metal rod in solution)
- Ag+ (aq) + e- –> Ag (s)
Metal ion based (metal block in solution)
- Fe+3 (aq) + e- –> Fe+2 (aq)
A non-metal gaseous (electrode in gas chamber)
- 2H+ (aq) + 2e- –> H2 (g)
- Cl2 (g) + 2e- –> 2Cl- (aq)

Question 12

What is NEO?

Answer 12

Negative Electrode is Oxidation

Question 13

How does concentration affect electrodes and cell potential? (diluting)

Answer 13

Diluting reduces concentration of blank
to oppose this equilibrium shifts left/right
Equation
less/more electrical energy produced by forward/backward reaction
cell potential decreases/inscreases

Question 14

How does concentration affect electrodes and cell potential? (increasing)

Answer 14

Increasing concentration of blank
to oppose this equilibrium shifts left/right
Equation
less/more electrical energy produced by forward/backward reaction
cell potential decreases/increases