Electrochemistry

Question 1

What is Electrolysis?

Answer 1

the breaking down of a compound into its elements using an electric current in aqueous or molten state

Question 2

Why is electrolysis often used?

Answer 2

• 1. to extract metals from metal ores
• 2. purify metals
• 3. produce non-metals

Question 3

complete the sentence:

Cations move to the [insert] charged electrode where they [insert] electrons, which is [insert]

Answer 3

1. negatively
2. gain
3. reduction

Question 4

What is observed if hydrogen is produced at the cathode?

Answer 4

bubbles

Question 5

Anions move to the [insert] charged electrode where they [insert] electrons, which is [insert]

Answer 5

1. postively
2. lose
3. oxidation

Question 6

Why are the ions formed at the electrodes different when a solution is aqueous or molten?

Answer 6

because when a solution is aqueous, water is present which contributes H+ and OH- ions

Question 7

Define relative electrode potential

Answer 7

How easily an ion is discharged during electrolysis

Question 8

What is the formula for electric charge

Answer 8

Q = I * t

where I is the electric current/A and t is the time/s

Question 9

What is one faraday

Answer 9

The amount of electric charge carried by 1 mole of electrons

Question 10

What is the formula for the relationship between faraday constant & avogadro constant?

Answer 10

F = L * e

where f is faraday’s constant, L is the avogadro’s constant & e is the charge on an electron

Question 11

What is the electrode when the electrode cell potential is less than 0?

Answer 11

Anode and its an oxidation reaction

Question 12

What is the electrode when the electrode cell potential is more than 0?

Answer 12

Cathode and its a reduction reaction

Question 12

What are the standard conditions for SHE (standard hydrogen electrode)?

Answer 12

• 298K (25c)
• 1 moldm-3 (H+)
• 1 atm (H2)

Question 13

How do you calculate the standard cell potential E(cell) ?

Answer 13

E(cathode) - E(anode)

Question 14

what does it mean when the standard cell potential is > 0

greater than 0

Answer 14

it means that the redox reaction is spontaneous under standard conditions

Question 15

what does it mean when the standard cell potential is < 0

less than 0

Answer 15

It means that the redox reaction is NOT spontaneous under standard conditions

Question 16

give the formula

What is the Nernest equation?

Answer 16

E = ( Eꝋ) - RT/NF * Log([red]/[ox])

Eꝋ is the standard electrode potential, R is gas constant, T is temp/K, Z is number of electrons transferred, F is faraday’s constant

Question 17

Which direction is the flow of the electrons?

Answer 17

from the negative pole to the positive pole

Question 18

T or F: A reaction that is spontaneous, is not feasible

Answer 18

FALSE, if a reaction is spontaneous it IS feasible

Question 19

What does a more positive SCP suggest?

STANDARD CELL POTENTIAL

Answer 19

• the species is easily reduced
• the species is better oxidising agent

Question 20

What does a less positive SCP suggest?

Answer 20

• the species is easily oxidised
• the species is a better reducing agent

Question 21

what is the difference between Eꝋ & E

Answer 21

E is the electrode potential used under non-standard conditions whilst Eꝋ is the standard electrode potential

Question 22

What is the formula for standard Gibbs free energy?

Answer 22

ΔGꝋ = - n x Ecellꝋ x F

ΔGꝋ is standard gibbs free energy, n is the number of electrons transferred, Ecellꝋ iis the standard cell potential, F is faraday’s constant

Question 23

What can farday’s constant be used to calculate?

Answer 23

• the mass of a substance deposited at an electrode
• the volume of gas liberated at an electrode

Question 24

What is the electrode (reduction) potential?

Answer 24

a value which shows how easily a substance is reduced

Question 25

What are the factors affecting the standard electrode potential?

Answer 25

- temperature - pressure of gases - concentration of reagents

Question 26

A reaction is more feasible when the Eꝋ is (+) or (-)? ## Footnote Eꝋ is a value which indicates how easily a species can get oxidised or reduced

Answer 26

positive (+) meaning easier to reduce the species

Question 27

How can standard free energy change be calculated?

Answer 27

ΔGꝋ = - n x Ecellꝋ x F

Question 28

What is meant by standard electrode potential

Answer 28

the voltage of an electrode compared to a standard hydrogen electrode at 1 moldm^3, 298K and 101kPa (standard conditions)