ANS:A - Electrolysis of water.

Electrolysis of water is a chemical process that uses electricity to split water molecules (H2O) into hydrogen (H2) and oxygen (O2) gases. It is a method of producing hydrogen gas from water, which can serve as a clean and sustainable source of hydrogen for various industrial applications, including ammonia manufacture. Here's how electrolysis of water works:

1. Setup: The electrolysis process typically takes place in an electrolysis cell, which consists of two electrodes (an anode and a cathode) immersed in a conductive solution of water, known as the electrolyte. The electrodes are usually made of inert materials like platinum or graphite.
2. Electrolyte: The electrolyte used in electrolysis of water is usually a dilute solution of sulfuric acid (H2SO4) or potassium hydroxide (KOH), which enhances the conductivity of water and facilitates the flow of electric current between the electrodes.
3. Electrical Current: A direct current (DC) electrical voltage is applied across the electrodes, causing water molecules to undergo electrolysis. The electrical current flows through the electrolyte, driving chemical reactions at the electrodes.
4. Electrochemical Reactions:
   • At the cathode (negative electrode), water molecules are reduced to hydrogen gas and hydroxide ions (OH-): 2𝐻2𝑂(𝑙)+2𝑒−→𝐻2(𝑔)+2𝑂𝐻−(𝑎𝑞)2H2​O(l)+2e−→H2​(g)+2OH−(aq)
   • At the anode (positive electrode), water molecules are oxidized to oxygen gas and positively charged hydrogen ions (protons, H+): 2𝐻2𝑂(𝑙)→𝑂2(𝑔)+4𝐻+(𝑎𝑞)+4𝑒−2H2​O(l)→O2​(g)+4H+(aq)+4e−
   • The net reaction for electrolysis of water is the overall decomposition of water into hydrogen and oxygen gases: 2𝐻2𝑂(𝑙)→2𝐻2(𝑔)+𝑂2(𝑔)2H2​O(l)→2H2​(g)+O2​(g)
5. Gas Collection: The hydrogen gas produced at the cathode and the oxygen gas produced at the anode are collected separately. Typically, the gases are bubbled through water to remove any traces of electrolyte or impurities before being collected.
6. Uses: The hydrogen gas produced by electrolysis of water can be used as a clean fuel for various applications, including hydrogen fuel cells, industrial processes (such as ammonia synthesis), and transportation (hydrogen-powered vehicles).

Overall, electrolysis of water provides a sustainable method for producing hydrogen gas without the use of fossil fuels, making it an attractive option for generating clean energy and reducing greenhouse gas emissions. However, the process requires significant electrical energy input, which can affect its overall efficiency and economic viability, particularly in regions with high electricity costs.