21: Oxidation and Reduction in Chemical Cells

Question 1

In what scenario should inert electrodes be set up in chemical cells?

Answer 1

When reactants and products cannot serve as the electrode material.

Question 2

List two common inert electrodes and explain why one is usually used.

Answer 2

Carbon and platinum, carbon is usually used because it is cheaper than platinum.

Question 3

How does the voltage of the chemical cell relate to the difference of positions of the chemicals in the electrochemical series?

Answer 3

The greater the difference in position in the electrochemical series, the larger the voltage produced.

Question 4

How can we identify the anode and cathode of a chemical cell?

Answer 4

The electrode at which oxidation occurs is the anode while the electrode at which reduction occurs is the cathode.

Question 5

What is the definition of a fuel cell?

Answer 5

A fuel cell is a chemical cell in which the reactants can be supplied continuously and the products of the cell reaction are continuously removed.

Question 6

What are the similarities between a fuel cell and a dry cell?

Answer 6

A fuel cell uses a chemical reaction to produce electrical energy like a dry cell. However, unlike a dry ell, it can be refueled continuously while dry cells cannot.

Question 7

What is the negative electrode of a hydrogen-oxygen fuel cell?

Answer 7

Porous graphite coated with nickel.

Question 8

What is the positive electrode of a hydrogen-oxygen fuel cell?

Answer 8

Porous graphite coated with nickel and nickel(II) oxide.

Question 9

What is the usage of the nickel and nickel(II) oxide coated on the electrodes of a hydrogen-oxygen fuel cell?

Answer 9

They act as catalysts for the reactions that occur on the surfaces of the electrodes.

Question 10

What is the electrolyte of an alkaline hydrogen-oxygen fuel cell?

Answer 10

Potassium hydroxide solution.

Question 11

Which side of a hydrogen-oxygen fuel cell is the cathode?

Answer 11

The side where oxygen is supplied, since oxygen undergoes reduction in the reaction.

Question 12

Which side of a hydrogen-oxygen fuel cell is the anode?

Answer 12

The side where hydrogen is supplied, since hydrogen undergoes oxidation in the reaction.

Question 13

What is the overall redox equation for a hydrogen-oxygen fuel cell?

Answer 13

2H₂+O_{2</sub -> 2H2O}

Question 14

List 4 advantages of using hydrogen-oxygen fuel cells.

Answer 14

1. Water is the only product and there are no pollutants formed.
2. It is an efficient way of converting chemical energy to electrical energy.
3. It does not need recharging.
4. It can have a range of sizes for different uses.

Question 15

List 5 disadvantages of using hydrogen-oxygen fuel cells.

Answer 15

1. It is expensive to produce them.
2. Hydrogen is difficult to be transported since it is explosive.
3. Hydrogen is difficult to be stored.
4. Hydrogen is produced using methane, which is a finite resource. Producing hydrogen using renewable resources is expensive.
5. It does not work well at low temperatures.