19.1 Electrochem

Question 1

What is the Electromotive Force (EMF) of a cell

Answer 1

the greatest potential difference that it can generate in volts

Question 2

what is the cell/electrode potential?

Answer 2

the potential generated when electrons flow from the electrode with the more negative potential to the electrode with the most positive potential

Question 3

What is Standard hydrogen electrode (SHE)

Answer 3

Baseline for measuring and comparing the electrode potentials of other half cells

Question 4

Outline the Standard hydrogen electrode

Answer 4

• Consist of an inert platinum as the conducting metal
• in contact with 1 mol dm-3 H ions (pH 0)
• The preassure of H2 is 100 kpa at 298 K
• 0 volts

Question 5

What is standard electrode Potential of a half cell ( E *)

Answer 5

• the measure of the reducing power of half cell in standard conditions, therefore the electrode’s element.
• measured by connecting the half cell to SHE and seeing how much electrons it pulls from SHE.

Question 6

what is the standard electrode also known as?

Answer 6

Standard reduction potential

Question 7

All E* value refer to what reaction?

Answer 7

reduction reaction

Question 8

E* value and number of electrons

Answer 8

Does not depend on the total number of electrons so don’t have to be scaled up or down according to coefficients

Question 9

The more positive the E* value for a half cell

Answer 9

the more readily it is reduced

Question 10

What value of E* cell signify the spontaneity of the reaction?

Answer 10

• Positive value

Question 11

What is the Electrolyte

Answer 11

Usually a molten ionic liquid or solution of an ionic compound.

Question 12

In aqueous solution what happens to water at the anode?

Answer 12

• Oxidized to oxygen

Question 13

In aqueous solutions what happens to water at the cathode?

Answer 13

• Reduced to hydrogen

Question 14

In a molten ionic electrolyte what are the ions present?

Answer 14

• only the ones form the ionic compound

Question 15

If there are multiple ions in the electrolyte how can you deduce which ion will be preferred for redox?

Answer 15

• Compare E*
• Concentrations of the ions in the electrolyte
• the nature of the electrode

Question 16

Why is electrolysis of aqueous solutions more complicated?

Answer 16

Either ions or water can go though redox

Question 17

What is selective discharge?

Answer 17

The discharge of an ion at the electrode opposed to water

Question 18

What is added to increases the electrical conductivity of water for electrolysis?

Answer 18

ionic compounds i.e NAOH

Question 19

When is it possible to have Cl be preferred for redox over water even though Cl has a lower E*?

Answer 19

at higher concentration of Cl.
-that’s how electrolysis of NaCl works

Question 20

What happens with electrolysis with copper electrodes?

Answer 20

• copper anode oxidizes itself, deteriorating in the process
• The Cu ions flow to the copper cathode and get reduced making the cathode bigger

Question 21

Factors affecting the yield of elecrolysis

Answer 21

• current
• duration of electrolysis
• Charge on the ion

Question 22

What is electroplating?

Answer 22

using electrolysis to coat a object with metal