Unit 3.1 - Redox and standard electrode potential (physicsandmathstutor))

Question 1

define oxidation in terms of electron transfer

Answer 1

loss of electrons

Question 2

define reduction in terms of electron transfer

Answer 2

gain of electrons

Question 3

what is a redox reaction

Answer 3

a reaction in which oxidation and reduction occur on different species simultaneously

Question 4

what is standard electrode potential

Answer 4

the potential across electrons when a redox system is connected to a hydrogen half-cell (under standard conditions)

Question 5

what are conditions required for measuring standard electrode potential

Answer 5

• 298K temperature
• 100kPa pressure
• 1.00mol/dm3 conc of ions

Question 6

why must metal electrodes be cleaned with sandpaper before creation of an electrochemical cess

Answer 6

to remove any metal oxide that has formed on the surface + improve conductivity

Question 7

describe movement of electrons in an electrochemical cell

Answer 7

electrons flow through the wire from + to - electrode

Question 8

why is a salt bridge used in an electrochemical cell

Answer 8

-maintain charge balance and complete the circuit

Question 9

why must salt be inert in the salt bridge

Answer 9

salt must be inert so that it doesn’t react with solutions
(cell potential would change if reactive salt was used)

Question 10

what moves across salt bridge

Answer 10

ions

Question 11

what rance of cell potential values is a process feasible

Answer 11

cell potential must be greater than 0

Question 12

how is cell potential calculated

Answer 12

(+)-(-)

Question 13

why might theoretical cell potential values be different to values obtained experimentally

Answer 13

conditions may be non-standard

Question 14

in an electrochemical cell, is the more negative half cell oxidised or reduced

Answer 14

oxidised

Question 15

what is a fuel cell

Answer 15

a cell that continually produces a voltage as long as it is supplied with oxygen and a fuel (like hydrogen)

Question 16

what is the only product of a hydrogen-oxygen fuel cell

Answer 16

water

Question 17

how does a hydrogen-oxygen fuel cell work

Answer 17

• hydrogen and oxygen are pumped through porous electrodes. The electrolyte is often an acid (phosphoric acid)
• hydrogen and oxygen react = energy + water

Question 18

what are the 2 half equations taking place in hydrogen-oxygen fuel cell

Answer 18

2H₂ + 4OH⁻ <–> 4H₂O + 4e⁻
O₂ + 2H₂O + 4e⁻ <–> 4OH⁻

Question 19

write an overall reaction that takes place in a hydrogen-oxygen fuel cell

Answer 19

2H₂ + O₂ –> 2H₂O

Question 20

3 advantages of using fuel cells

Answer 20

• no pollution
• produce more energy than alternative fuel (like petrol)
• process is continuous as long as fuel is supplied

Question 21

4 disadvantages of using fuel cells:

Answer 21

• expensive materials
• hydrogen is hard to store
• efficiency effected by temp
• high pressure tanks needed