Conduction of Electricity in Liquids

Introduction

Electricity is the movement of electrons from one point to another point in a conductor. Conduction of electricity takes place in all three states of matter such as solid, liquid, and gas. The mechanism of conduction of electricity in liquid is different than in solid. We will try to understand the conduction of electricity in liquid by studying an example of pure water.

How Does Liquid Conduct Electricity?

Pure water is a bad conductor of electricity. Then how does it conduct electric current? We have to add salts in pure water for conduction.

Let us take an example of sodium chloride salt in pure water. The sodium chloride breaks its bond and dissolves in water. Sodium chloride separates into sodium ion $\mathrm{(Na^+)}$ and chloride ion $\mathrm{(Cl^-)}$ after passing an electric current through it. The sodium ion is a positively charged ion. It is known as a cation. The chloride ion is a negatively charged ion. It is called an anion.

These ions carry electric current. In the following diagram, we can see the sodium ions have moved towards the negatively charged electrode i.e. cathode while chloride ions have moved towards the positively charged electrode i.e. anode. Sodium ions gain electrons from the cathode. The formation of sodium atoms takes place. Chloride ions donate electrons to the anode and form chlorine gas. The sodium atoms and chlorine gas are stable. Both the ions are deposited into the electrodes. The conduction of electricity in liquid is done by this process. This process is also known as electrolysis.

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Electrolysis in Water

Electrolysis is a process in which a chemical change is produced in a substance by passing an electric current through it. It involves breaking the water molecules $\mathrm{(H_2O)}$ into hydrogen gas and oxygen gas due to electric current. Pure water is taken for this experiment. As we have seen pure water does not conduct electric current so salts are added to it. Platinum electrodes are immersed in water. The electric current is passed throughout the solution.

The water is split into a hydrogen ion $\mathrm{(H^+)}$ and a hydroxide ion $\mathrm{(OH^-)}$.

$$\mathrm{H_2O=2H^++OH^-}$$

The hydrogen ions move towards the cathode and the hydroxide ion moves toward the anode.

Reduction at cathode

The hydrogen ions move towards the cathode. They gain electrons from the cathode and convert them into stable hydrogen gas.

$$\mathrm{H_2O=2H^++OH^-}$$

$$\mathrm{2H^+(aq)+2e^-\rightarrow H_2(g)}$$

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Oxidation at Anode

The hydroxide ions move towards the anode. They lose an excess electron to the electrode and convert them into stable oxygen gas.

$$\mathrm{4H_2O\rightarrow 4OH^-(aq)+4H^+}$$

$$\mathrm{4OH^-(aq)\rightarrow O_2(g)+2H_2O(I)+4e}$$

In the electrolysis of water, one molecule of oxygen is produced for every two molecules of hydrogen. The ratio of hydrogen and oxygen molecule is 2:1. Electrolysis is mainly used for the extraction of metals from their ores.

Electroplating

It is the process of coating one metal to another metal by passing an electric current into the solution. It is mainly done to prevent the corrosion of metals.

Cathode and Anode

Electroplating is carried out in an electrolytic cell. Electric current is applied externally in it. A cathode is an electrode connected to the positive terminal of the battery. The anode is also an electrode connected to the negative terminal of the battery. The material to be electroplated is placed as a cathode. The metal which is going to electroplate is placed as the anode. The salt solution of metal is used for deposition.

Silver plating

The material to be coated acts as a cathode. The piece of silver acts as an anode and the silver nitrate solution acts as an electrolyte. The silver ions get deposited on the cathode after passing an electric current through the electrolytic solution. The impurities get deposited on the anode.

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Applications of Electroplating

• The technique of electroplating is used in jewellery design. The less expensive metals are coated with gold and silver metal to make them attractive. These gold or silver-plated ornaments are less expensive than the actual ornaments of gold and silver.

• Iron is used to construct bridges. It is also used in automobiles to provide strength. But rusting of iron may occur due to moisture present in the air hence it is coated with zinc metal.

• The appearance of chromium metal is shiny. Chromium plating is done on kitchen gas burners, car parts, wheel rims, bicycle handlebars, bath taps, etc.

• Electroplating is also used in the conduction of electricity. Integrated circuits are placed in cell phones and computers. Gold and silver are good conductors of electricity. But due to its high prices, it cannot be placed in integrated circuits of computers and cell phones. So, the coating of silver and gold is applied to less expensive metals. It helps in the conduction of electricity.

• The electroplating technique is also used to coat cans used to store food. Cans are made up of iron. Iron is coated with tin because it is less reactive than iron. The food does not come in direct contact with iron and the spoilage of food is prevented.

Facts about Electrolysis and Electroplating

• The term 'electrolysis' was coined by Michael Faraday.

• Electrolysis is used to clean coins and other metals.

• Electrolysis is used to obtain substances like magnesium, calcium, chlorine, aluminium, sodium chlorate, potassium chlorate, etc.

• Electroplating was invented by an Italian chemist called Luigi Brugnatelli in 1805. This technique is more than 200 years old.

• Electroplating is the most common technology for metal plating because it controls the thickness of plating.

• In the kitchen, we use stainless steel utensils. They are coated with copper by electroplating.

Conclusion

Conduction of electricity in liquids mainly occurs in electrolysis and electroplating. The electroplating process plays an important role in jewellery making. Electrolysis is an important process for the purification of metals. These techniques require a large amount of electricity. The management of waste products generated by electroplating and electrolysis is difficult. Though these techniques have some disadvantages it is still used commercially due to their benefits.

FAQs

Q1. Define electrolysis.

Ans. It is the process in which chemical changes are produced in electrolytes due to the passage of electric current.

Q2. Define electroplating.

Ans. It is the process of coating one metal on another metal by the passage of an electric current in the electrolytic solution.

Q3. Prepare a list around you that is electroplated.

Ans. Gold plating: Gold is coated on silver ornaments. They are called gold-plated ornaments.

Zinc plating: Iron is used in construction. It is coated with zinc to avoid rusting and corrosion.

Q4. What are ionic compounds?

Ans. The compounds that dissociate in water completely are known as ionic compounds.

Q5. What is an ion?

Ans. The atom forms a charge on gaining or losing electrons is known as an ion.