Chemical effects of Electric current: Electroplating & Metal Extraction

Current is produced by the flow of electrons through the wire. We are often cautioned against touching electrical appliances with wet hands. But ever wondered why it is dangerous to touch an electric appliance with wet hands. We know that there are certain materials that allow electricity to pass through them easily, they are called conductors. On the other hand, the materials which do not allow electricity to pass through them easily are called insulators. But they are always in solid form, what happens if they are liquid? Do water conduct electricity? Actually, freshwater is not a good conductor of electricity. The dissolved salts present in water are good conductors of electricity, therefore the presence of a small amount of salt in the water makes it a conductor. There is a wide variety in conductivity of various types of liquids due to different proportions of salts dissolved in them. Due to this, it is advised to stay away from electric poles during the rainy season. In this article, we will learn more about the chemical effects of electric current.

Read Also: Combination of Resistors-Series and Parallel

Key Takeaways: Electric current, current in liquid, electrodes, electrolytes, electroplating, metal extraction, metal purification

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Chemical effects of electric current

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When we pass an electric current through a conducting solution, a chemical reaction takes place. When we pass an electric current through water, water ionizes into H⁺(aq) and OH^- (aq) ions. The H⁺(aq) ions go towards the cathode to gain electrons and the OH^-(aq) go towards the anode to lose electrons. H₂(g) is evolved at cathode and O₂(g) is evolved at the anode.

Check Important Notes for Cells in Series and in Parallel

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Effect of current in the liquid

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When current is passed through the liquid solution, a chemical reaction takes place. Some chemical reactions include -

• Gas bubble formation at electrodes
• Metal deposition on electrodes
• Change of color of the solution

Not all liquids conduct electricity. Saltwater is a good conductor of electricity but freshwater is a bad conductor. Water containing dissolved salts or minerals are found to be good conductor of electricity. When electricity is passed through electrolytes, its constituents break into positive and negative ions. The ions help in carrying current through the liquid. More the number of ions, the more is its conductivity. 

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Experiment to check whether liquid conducts electricity

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To check whether liquid conducts electricity, we conduct the following experiment:

Procedure:

• Connect two wires to the cell.
• Take a bowl of saltwater and freshwater.
• Connect the wires to an LED such that the circuit has two open ends.
• Dip the two wires first in freshwater and then in saltwater.
• The brightness of LED tells whether the liquid is a good conductor or not.

Observation: You will observe that LED glows dimly in freshwater while it glows brightly in saltwater.

Conclusion: Liquids containing acid, bases, minerals make the liquid more conducting, that's why it is not safe to touch electrical appliances with wet hands.

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Electrodes and electrolytes

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An electrode is a conductor which makes contact with nonmetallic parts of a circuit such as an electrolyte, semiconductor, etc. If it is in an electrolytic cell then it is called anode or cathode. An anode is an electrode that is connected to the positive side of a cell and a cathode is connected to the negative side of the cell. 

The electrolyte is a liquid that conducts electricity and also forms ions when an electric current is passed through it. The most common electrolytes are salts, acids, bases which ionize when dissolved in water. 

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Applications of chemical effects of electric current

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The applications of chemical effects of electric current are:

Electroplating

Electroplating is the process of coating a metal with another metal layer through electrolysis. It is widely used in industries for various purposes. One metal having a specific property is coated over a metal that lacks that property to obtain the required combination. 

For example, chromium is electroplated on bicycle handlebars, kitchen gas burners, etc because chromium has a shiny appearance, it doesn’t corrode, resists scratches, etc. Chromium is expensive so it is not economical to use chromium to make these objects, rather coating chromium over a cheap metal also does the work.

Read More: Cells, emf, Internal Resistance

Electroplating in the lab

According to the requirement, the right and left electrodes are chosen. If we want to deposit gold over a metal then the chosen electrolyte must be of gold and one electrode should be of gold and another one should be of the metal on which gold is to be coated.

Applications of electroplating

The applications of electroplating are:

1. The most extensive use is in the jewellery industries where layers of silver or gold are coated.
2. Parts of bicycle and gas burners are electroplated with chromium to prevent rusting.
3. Iron is coated with tin to make tin cans.
4. Zinc coating prevents corrosion of steel objects.
5. The pillars of the bridge and electric poles are electroplated with a layer of zinc.
6. Chrome plating and anodizing are used to prevent corrosion.
7. Car parts are electroplated with chromium to give a shiny texture.

Metal extraction

Metals can be extracted from their respective ores. When electricity is passed through ores, they break down into ionic lattices. Hence metals can be separated from it. Some metals which are extracted in this method are - sodium, magnesium, calcium, potassium, etc. 

Read Further: Ohm’s Law And its Limitations

Metal purification

Metals are purified by various methods. Electrorefining is one of the methods where the electrolytic cell is used. The impure metals is used as anode and cathode is the pure form of the same metal. When electric current is passed, the metal is stripped off of impurities and gets deposited on the cathode. Metals such as zinc, copper, aluminium are purified by this method.

Check More: Resistor Colour Codes

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Things to remember

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1. Current is produced by the flow of electrons through the wire.
2. When current is passed through the liquid solution, a chemical reaction takes place.
3. Saltwater is a good conductor of electricity but freshwater is a bad conductor.
4. When electricity is passed through electrolytes, the constituents break into positive and negative ions.
5. An electrode is a conductor which makes contact with nonmetallic parts of a circuit such as an electrolyte, semiconductor, etc.
6. Parts of bicycle and gas burners are electroplated with chromium to prevent rusting.
7. Zinc coating prevents corrosion of steel objects.
8. Electrorefining is one of the methods where electrolytic cell is used to extract metal from ores.

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