Electrochemistry

Question 1

What is electrolysis

Answer 1

The breakdown of an ionic compound, molten or in aqueous solution, by the passage of electricity.

Question 2

What are electrodes

Answer 2

The solid electric conductor through which an electric current enters or leaves an electrolytic cell. They are usually made of graphite (carbon) or platinum as these materials are inert (unreactive).

Question 3

What is a cathode

Answer 3

The negative electrode of an electrolytic cell. It gets charged up with electrons which flow from the negative terminal from the battery.

Question 4

What is an anode

Answer 4

The positive electrode of an electrolytic cell.

Question 5

What is an electrolyte

Answer 5

Usually an ionic compound that when molten or aqueous is ionised and so conducts electricity. Essential for electrolysis.

Question 6

What are the three main components of the electrolytic cell

Answer 6

a battery

two electrodes , one of which is connected to the negative terminal of the battery (cathode ) as the negative electrode

and the other connected to the positive terminal (anode ) as the positive electrode

an electrolyte (aqueous or molten substance that conducts electricity).
The

Question 7

What are the main stages in electrolysis

Answer 7

1. The electrolyte is made molten (melted through heating) or dissolved in water to give an aqueous solution.
2. An electric current is passed through the cell.
3. Cations (metal ions or hydrogen ions) move towards the negatively charged cathode.
4. Anions (non-metal ions) move towards the positively charged anode.
5. The cations come from the metal ions. For example, in the electrolysis of molten sodium chloride, NaCl, the cation is the sodium ion which will gain an electron to form solid sodium metal.
6. The anions come from the non-metal ions, in the case of molten sodium chloride, the chloride ion loses an electron to form chlorine gas.

Question 8

What other way can you think about the electrodes in terms of oxidation and reduction

Answer 8

1. Electrons flow from the negative terminal of the battery and charge up the cathode with negative charge.
2. This will attract the cations (positive ions) and make them move towards the cathode (negative electrode) to gain electrons (reduction).
3. The anions (negative ions) move towards the anode with positive charge and lose electrons (oxidation).
4. Electrons flow from the anode (positive electrode) to the cathode (negative electrode).

Question 9

What is the product at the cathode and anode and the observations of the electrolyte bromide

Answer 9

Cathode - lead
Anode - bromine
Observation - silvery solid at the cathode - brown gas at the anode

Question 10

What is the product at the cathode and anode and the observations of the electrolyte aqueous sodium chloride

Answer 10

Cathode - hydrogen
Anode - chlorine
Observation - colourless gas at cathode, which makes a lighted splint go ‘pop’ - pale yellow-green gas at anode, which turns universal indicator red - pale yellow-green gas at anode also bleaches red litmus paper as chlorine is an acidic gas

Question 11

What is the product at the cathode and anode and the observations of the electrolyte dilute sulfuric acid

Answer 11

Cathode - hydrogen
Anode - oxygen
Observation - colourless gases at both electrodes - cathode gas makes a lighted splint go ‘pop’ - anode gas relights a glowing splint

Question 12

What ia the effect of dilution

Answer 12

If a dilute solution of aqueous sodium chloride solution is electrolysed, the products can change.

Question 13

What is eletroplating

Answer 13

Coating one metal with a thin layer of another metal either to improve the appearance of an object or to prevent corrosion.