Electrolysis of Water
How does electricity conduct in liquids? We know that under solids metals are the best electricity conductors. That is due to loosely held outermost mobile electrons that move from one atom to another. On the contrary, electrons in a chemical bond of liquids are static. Charges introduced by dissolving compounds in the water are responsible for the conduction of electricity in liquids. In water, the chemical bond of compound breaks into numerous atoms carrying a positive or negative charge on it. Freely moving charges flow resulting in electrical conductivity.
Electrolysis or How do Liquids Conduct Electricity?
The phenomena of chemical decomposition of liquid or solution constituting ions when electricity passed through it are called electrolysis. The compounds which break its chemical bond in water are called Ionic compounds. Are you thinking of an example; Sodium Chloride is an excellent example of an ionic compound. Atoms carrying charges are called Ions. Positive charge-carrying ion is called cations. Negative charge-carrying ions are called anions. Now if you mix Sodium Chloride in water, freely moving ions are formed. Cations travel to a negative electrode to collect electrons. Anions navigate to the positive electrode and donate its extra electrons.
If you have a query in your mind - what happens when electricity passes compounds in the molten state, then here is the answer – molten metal compound splits into single component form and gets accumulated at electrodes. Gases released as the result of this chemical reaction dissipates in the air. Now let’s move ahead and understand what happens when electricity passes in water.
Now let’s move ahead to understand what happens when electricity passes in water.
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Image of electrolysis of water displaying split of water in hydrogen and hydroxide ion moving towards cathode and anode respectively to release hydrogen and oxygen gas.
Electrolysis in Water
Let’s observe how electrolysis of water happens. The water dissociated into hydrogen and oxygen gas when the electric current passed through it. An electronic source connected to an inactive electrode like platinum immersed in water. Does pure water conduct electricity? Pure water is the best insulator. Therefore, an electrolyte was added to improve the conductivity of pure water. When electric power passes, the water separates into positive hydrogen ions and negatively charged hydroxide ions. Now, what happens to the charged ions?
H₂O = 2H⁺ + OH⁻
The two charged ions traverse towards opposite electrodes. Electron transfer from a negatively charged electrode, i.e. cathode to hydrogen ion leading to a reduction of the cathode. Whereas the positively charged electrode, i.e. anode gains an electron from hydroxide ion resulting in oxidation of anode.
Reduction at Cathode
The hydrogen ions move towards the cathode. These positive cations gain an electron from the cathode and convert into stable hydrogen gas.
H₂O = 2H⁺ + OH⁻
2 H⁺(aq)+ 2e⁻ → H₂(g)
Oxidation at Anode
Whereas, the negative hydroxide anion moves towards the anode. This negative anion loses an excess electron to the electrode and converts into stable oxygen gas.
4 H₂O → 4 OH⁻(aq) + 4 H⁺
4 OH⁻ (aq) → O₂ (g) + 2 H₂O (l) + 4 e
The ratio of generated oxygen and hydrogen molecules is 2:1. The electrolysis of water produces one molecule of oxygen for every two molecules of hydrogen. Thus twice the volume of hydrogen is generated as a result of water electrolysis.
Testing the electrical conductivity of liquids can be done by the same mechanism. Take a fluid in a container which has two electrodes connected to battery and bulb. The glowing bulb will indicate that fluid is a good conductor of electricity.
Benefits of Electrolysis
Generation hydrogen for fuel, or the production of electric power using fuel cells
Production caustic soda from the concentrated saline solution.
One of the most critical uses of electrolysis is the production of heavy metals like aluminium, sodium, calcium. During the electrolysis of molten compounds, heavy metals get precipitated at the electrode. Precipitated metal is collected and used for different industrial purposes.
Another important use of electrolysis is the coating of one metal over another. The method used to coat a metal over another is called electroplating. The object to be coated with metal is used as a cathode. The anode is made of metal used for coating. The electrolyte is the soluble compound of metal to be coated.
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Image of the basic setup of electroplating to coat spoon which is made as cathode ,whereas anode is made of the metal which is used for coating.
Fascinating and Fun Fact with Regards Conduction of Electricity in Liquids
Have you got skin with plenty of hair? Then visit beauty shops and get rid of extra hairs. Experts often use electrolysis to remove hair.
Did you know that gold jewellery is made? Solid gold electrolyzed to make jewellery.
Stainless steel cutleries in our kitchen like the spoon, fork, etc. are coated with copper by the process of electrolysis.
Utensils used in the religious places is electroplated to convert into expensive silver utensils.
FAQs on Conduction of Electricity in Liquids
1. What is meant by the conduction of electricity in liquids?
The conduction of electricity in liquids is the process where an electric current flows through a liquid medium. Unlike solid conductors like metals where the current is carried by free electrons, in liquids, the current is carried by the movement of charged particles called ions. This typically happens when a substance called an electrolyte is dissolved in a solvent (like water), causing it to break apart into positive (cations) and negative (anions) ions.
2. Why does electricity in liquids conduct through ions and not free electrons like in metals?
The mechanism of conduction is fundamentally different. In metals, atoms are in a fixed lattice, and their outermost electrons are delocalised, forming a 'sea' of free electrons that can move easily when a voltage is applied. In most conductive liquids (electrolytic solutions), electrons are tightly bound within molecular or ionic compounds. Conduction only occurs when these compounds dissociate into mobile ions. These ions, not free electrons, then move towards the oppositely charged electrodes to transport charge.
3. What are some common examples of liquids that conduct electricity?
Liquids that conduct electricity are typically solutions containing electrolytes. Some common examples include:
- Saltwater: A solution of sodium chloride in water.
- Lemon Juice or Vinegar: Acidic solutions that contain hydrogen ions.
- Tap Water: Contains dissolved minerals and salts, which provide ions.
- Copper Sulphate Solution: Used in electroplating experiments.
In contrast, liquids like distilled water, sugar solution, and oil are poor conductors.
4. Why is pure (distilled) water a poor conductor of electricity, while tap water can be a good conductor?
Pure water is a very poor conductor because it contains an extremely low concentration of ions. Water molecules (H₂O) only slightly self-ionise into H⁺ and OH⁻ ions. However, tap water is a good conductor because it is not pure; it contains various dissolved salts and minerals from its source. These impurities dissociate into a significant number of free-moving ions, which allow electricity to flow through it easily.
5. What is the difference between an electrolyte and a non-electrolyte?
The key difference lies in their ability to form ions in a solution. An electrolyte is a substance that, when dissolved in a solvent like water, dissociates into ions and creates an electrically conductive solution. Examples include salts, acids, and bases. A non-electrolyte is a substance that does not form ions when dissolved and therefore its solution does not conduct electricity. A common example is sugar (sucrose) dissolved in water.
6. How does dissolving a substance like common salt (NaCl) in water enable it to conduct electricity?
When common salt (Sodium Chloride) is dissolved in water, its ionic bonds are overcome by the water molecules. This process, called dissociation, causes the salt to break apart into its constituent ions: positively charged sodium ions (Na⁺) and negatively charged chloride ions (Cl⁻). These ions are now free to move throughout the solution. When electrodes are placed in the solution and a voltage is applied, the positive Na⁺ ions move to the negative electrode (cathode) and the negative Cl⁻ ions move to the positive electrode (anode), creating an electric current.
7. What is electrolysis and what are its important real-world applications?
Electrolysis is the process of using a direct electric current to drive an otherwise non-spontaneous chemical reaction. It is a major application of electrical conduction in liquids. Important applications include:
- Electroplating: Coating a thin layer of one metal onto another (e.g., chrome plating on car parts).
- Extraction of Metals: Extracting highly reactive metals like aluminium and sodium from their ores.
- Purification of Metals: Refining metals like copper to a very high purity.
- Production of Chemicals: Manufacturing essential chemicals like chlorine gas and sodium hydroxide from saltwater.
8. How can you perform a simple test to check if a liquid is a conductor of electricity?
You can build a simple circuit called a conductivity tester. This involves a battery, a small LED bulb, and two electrodes (like iron nails or graphite rods) connected in series. To test a liquid, you dip the two electrodes into it, ensuring they do not touch each other. If the liquid is a conductor, it will complete the circuit, and the bulb will light up. If the bulb does not glow or glows very dimly, the liquid is a poor conductor or an insulator.
