Chapter 1 - History

Question 1

How is a Leyden jar designed?

Answer 1

A glass jar with a conducting tin foil coating the inner and outer surface. Stops far enough down to prevent arcing between the foils. A rod penetrates the stopper of the mouth of the jar, and is electrically connected (usually by chain) to the inner foil.

The jar is charged by an electrostatic generator connected to the inner electrode, while the outer foil is grounded. Inner and outer surface stores equal but opposite charges.

Question 2

Who coined the term “battery”?

Answer 2

Benjamin Franklin - as a term for combining several Leyden jars

Question 3

Who was the first to connect several Leyden jars in parallel to increase the total stored energy?

Answer 3

Danial Gralath

Question 4

According to Faraday, how many Leyden jars would be required to electrolyse a grain of water?

Answer 4

~800.000

Question 5

Is a Leyden jar a battery?

Answer 5

No, a capacitor.

Question 6

What is the nature of the dispute between Luigi Galvani and Alessandro Volta on the nature of electricity?

Answer 6

Galvani held the view that twitching of the frog’s leg was due to electricity generated by living tissue.

Volta thought the twitching was caused by electricity generated from a physical cause, not from the life of the frog.

Question 7

What settled the dispute between Volta and Galvani on the nature of electricity?

Answer 7

The construction of the Voltaic pile. This showed that elecitricity was not something solely generated by living things.

Question 8

Who is considered the inventor of the electrochemical battery?

Answer 8

Alessandro Volta

Question 9

What was the Votalic pile?

Answer 9

A stack of discs of two metals - silver and zinc. The discs were separated by a piece of cloth or cardboard that has been soaked in salt water. This stack would create a small electric current that could be drawn off through wires and used for experiments.

Question 10

Where does the energy for the Voltaic pile come from? (ie. how is it charged?)

Answer 10

Through the purification of elements. The reactions during discharge are spontaneous and we require energy to reform the pure metals.

Question 11

What was the limiting factor that killed the Voltaic pile?

Answer 11

Hydrogen bubbles forming and reducing contact.

Question 12

What is reduction?

Answer 12

A chemical species gaining an electron (positive charge is reduced).

Question 13

What is oxidation

Answer 13

A chemical species is loosing an electron (positive charge is increased)

Question 14

What is the positive electrode?

Answer 14

The electrode with the highest electrical potential (during discharge) and where a positive charge would have the highest energy. Source of positive charge.

Question 15

What is the negative electrode?

Answer 15

The electrode with the lowest electrical potential (during discharge), where a positive charge would have the lowest energy. Source of negative charge.

Question 16

What is the anode?

Answer 16

The electrode where the oxidation occurs. Electrons leaves the anode.

Question 17

What is the cathode?

Answer 17

The electrode where the reduction occurs. Electrons enters the cathode.

Question 18

What is the source of confusion between the term “negative electrode” and “anode”, and “positive electrode” and “cathode”?

Answer 18

We usually talk exclusively cathodes and anodes during both charge and discharge. The terminology is technically only correct during discharge.

Since the cathode and anode are defined from what type of reactions occurs, what we usually term the “cathode” is actually, by definition, the anode during charge.

However, what we call a cathode is always the positive electrode, so a more correct term would be to call the cathode the positive electrode, and the anode the negative electrode.

Question 19

Describe the setup of a typical lemon battery experiment.

Answer 19

Use electrodes of different metals, e.g. zinc and copper. Connect in a lemon and hook up to a multimeter.

On the zinc side the following reaction is happening:
Zn -> Zn2+ + 2e-

The electrodes move through the current and reacts with H+ ions (from the citric acid) to form H2-gas:
2H+ + 2e- -> H2

Modifications:

1) Show that you short the battery by letting the electrodes touch.
2) Switch to a potato to show that other things functions as electrolyte as well.
3) Change to beaker - gather the hydrogen formed at the cathode. Put on fire.
4) Add zinc salt to prove that zinc participates in the reaction.
5) Add copper salt to prove that copper is not involved in the reaction.
6) Change metals for the electrode to notice changes in voltages.
7) Change the surface area of the electrodes to notice changes.
8) Notice changes over time.

Question 20

What is Faraday’s big contribution to electrochemistry?

Answer 20

His quantification of the relation between the mass of the materials involved and the total charge transferred. This meant that an electrochemical battery has a limited charge.

Question 21

What is Faraday’s 1st Law of Electrolysis?

Answer 21

The mass of a substance altered at an electrode during electrolysis is directly proportional to the quantity of electricity transffered at that electrode.

Question 22

What is Farday’s 2nd Law of Electrolysis?

Answer 22

For a given quantity of direct current electricity, the mass of an elemental material altered at an electrode is directly proportional to the element’s equivalent weight.

Question 23

Describe the Daniell cell.

Answer 23

Consists of copper and zinc electrodes immersed in solution of copper(II) sulfate (CuSO4) and zinc sulfate (ZnSO4) respectively. Originally sulphuric acid was used instead of zinc sulfate.

The two containers are connected by a salt bridge.

At the anode we get the oxidation: Zn -> Zn2+ + 2e-
At the cathode we get the reduction: Cu2+ + 2e- -> Cu

Question 24

What is a gravity cell?

Answer 24

A version of the Daniell cell where the electrolytes are separated by gravity due to their different densities. Became the industry standard for the electric telegraph.

Question 25

How did the early electrical telegraphs function?

Answer 25

Multiple wires to represent letters and numerals. Sent currents through sequentially, which would cause the acids on the recipients end to electrolyse (H2 bubbles formed). This would then be noted down and form the message.

Question 26

Who invented the lead acid battery? What was special about it?

Answer 26

Gaston Planté, in 1859. It was the first rechargeable battery.

Question 27

Describe a basic lead acid battery setup.

Answer 27

Consist of a lead anode and a lead dioxide cathode. These are immersed in a sulphuric acid. Both electrodes react with the acid to form lead sulphate, but the reaction at the lead anode releases electrons and the reaction at the lead oxide cathode consumes electrons.

Question 28

What was the first commercial breakthrough of the lead acid battery?

Answer 28

The Faure cell (invited by Camille Faure). The cathode used a lead oxide paste smeared on a lead grid.

Question 29

What were some of the limitations of the early lead-acid batteries (Faure cell and descendants)?

Answer 29

Liquid electrolyte limited the orientation of the battery.

Evaporation of water from the electrolyte required refilling.

Question 30

When was the first electric car made?

Answer 30

1884 in London. In the US, around 1890 by William Morrison.

Question 31

What was the Leclanche cell?

Answer 31

A cell which resolved conductivity issue with oxide electrode (in this case manganese oxide cathode) by mixing in carbon.

Question 32

What was the configuration of the dry cell?

Answer 32

The dry cell (Carl Gassner 1886) was a modification of the Leclanche cell. It was known as a dry cell because it did not have a free liquid electrolyte. It used ammonium chloride mized with Plaster of Pair to create a paste, with a small amount of zinc chloride added. Manganese dioxide cathode was dipped in the paste, and eveything was sealed in a zinc shell which acted as the anode.

Question 33

What was the advantage of the dry cell?

Answer 33

• More solid.
• Did not require maintenance
• Did not spill
• Could be used in any orientation

Question 34

What are the alkaline batteries?

Answer 34

The alkaline batteries employed alkaline electrolyte instead of acidic electrolytes.

The most common types are the Ni-Cd and Zn-MnO chemistries. Dry cells of the latter are the ones typically thought of as alkaline batteries today.

Question 35

Describe the NiCd battery

Answer 35

Rechargeable battery that uses a nickel oxide hydroxide and cadmium metal as electrodes. Originally invented in Sweden by Waldemar Jungner in 1899. In America patented by Edison as Ni-Cd or Co-Cd in 1902.

Rapidly lost market share to NiMH and Li-ion batteries in 90s. Concerns about Cd-toxicity.

Question 36

Describe the alkaline dry batteries

Answer 36

Primary batteries using Zn and MnO2 as electrodes. Large market share in primary batteries today.

Question 37

Describe the NiH2 batteries.

Answer 37

Originally developed for space applications. Functions as a quasireversible hydrogen-oxygen electrochemical cell. Oxygen is stored in the positive electrode as nickel oxyhydroxide and hydrogen being stored as high-pressure gas.

High energy density, extremely long lifetime. Been replaced by Li-ion in space applications now, due to higher energy density.

Question 38

Describe the NiMH batteries.

Answer 38

Similar to NiCd, but using a metal hydride as electrode instead of cadmium.

Question 39

When did experimentation with lithium begin?

Answer 39

In 1912 by G.N. Lewis