Section 8 - Electrode Potentials and Cells

Question 1

What is an electrochemical cell made from?

Answer 1

Two different metals dipped in salt solutions of their own ions and connected by a wire.

Question 2

What kind of reaction occurs in an electrochemical cell?

Answer 2

Redox

Question 3

What is the salt bridge made from and what is its use?

Answer 3

Filter paper soaked in KNO_3(aq)

Allows ions to flow and completes the circuit

Question 4

Which way do electrons flow round a circuit?

Answer 4

From the more reactive metal to the less reactive one

Question 5

What is the voltage between the two cells called?

Answer 5

Cell potential or EMF

Question 6

What kind of electrode is used if not the metal of the ions?

Answer 6

Platinum

Question 7

Is the forward direction of an electrode half equation showing reduction or oxidation?

Answer 7

Reduction

Question 8

What kind of electrode potential will a metal which is difficult to oxidise have?

Answer 8

Very positive

Question 9

If an electrode has a more negative electrode potential, will it be reduced or oxidised?

Answer 9

Oxidised

Question 10

Which half equation needs to be reversed?

Answer 10

The one for oxidation

Question 11

What are electrode potentials measured against?

Answer 11

Standard hydrogen electrodes

Question 12

Define Standard Electrode Potential

Answer 12

The voltage measured under standard conditions when the half-cell is connected to a standard hydrogen electrode

Question 13

What are the standard conditions for measuring electrode potentials?

Answer 13

• solutions have concentrations of 1.00 moldm^-3
• 298K
• 100kPa

Question 14

Where are the best oxidising agents found on an electrochemical series?

Answer 14

Left of the more positive end.

Question 15

Where are the best reducing agents found on an electrochemical series?

Answer 15

On the right of the more negative end

Question 16

How do you calculate Standard Cell Potential for two half-cells?

Answer 16

E_cell = E_reduced - E_oxidised

Question 17

How do you draw an Electrochemical cell?

Answer 17

Reduced Form | Oxidised Form || Oxidised Form | Reduced Form

Question 18

On which side of an electrochemical cell drawing does the half-cell with the more negative EMF go?

Answer 18

Left

Question 19

For a feasible reaction, is E_cell positive or negative?

Answer 19

Positive

Question 20

Are Lithium batteries rechargeable?

Answer 20

Yes

Question 21

What are the half-equations for the Lithium Cell?

Answer 21

Li⁺ + e^- <–> Li - negative electrode

Li⁺ + CoO₂ + e^- <–> Li⁺[CoO₂]^- - positive electrode

Question 22

How are lithium cells recharged?

Answer 22

A current is supplied to force electrons to flow in the opposite direction around the circuit and reverse the reactions.

Question 23

What are the reactions that occur in an alkaline hydrogen-oxygen fuel cell?

Answer 23

2H₂ + 4OH^- –> 4H₂O + 4e^-

O₂ + 2H₂O + 4e^- –> 4e^- + 4 OH^-

Question 24

What is the overall equation of alkaline hydrogen-oxygen fuel cell?

Answer 24

2H₂ + O₂ –> 2H₂O

Question 25

What are 3 advantages of fuel cells?

Answer 25

• more efficient - internal combustion engines lose energy through heat
• only waste product is water
• don’t need to be recharged

Question 26

Give 2 disadvantages of fuel cells:

Answer 26

• energy required to produce the hydrogen and oxygen - not carbon neutral
• hydrgoen is highly flammable