a. During electrolysis of NaOH, Cl2 and H2 while for molten NaCl only Na metal and Cl2 gas are obtained. Explain these observations with suitable eqn. b. Electrolysis of conc. and dil. sulphuric acid are different. Explain with eqn.

Electrolysis is a fascinating process that involves breaking down compounds into their constituent elements using electricity. Your question touches on two distinct scenarios: the electrolysis of sodium hydroxide (NaOH) and molten sodium chloride (NaCl), as well as the differences in electrolysis between concentrated and dilute sulfuric acid (H2SO4). Let’s break these down step by step.

Electrolysis of Sodium Hydroxide (NaOH) and Molten Sodium Chloride (NaCl)

When we perform electrolysis on sodium hydroxide, the solution dissociates into sodium ions (Na⁺) and hydroxide ions (OH^-). At the anode (the positive electrode), oxidation occurs, leading to the formation of chlorine gas (Cl₂), while at the cathode (the negative electrode), reduction takes place, producing hydrogen gas (H₂). The overall reactions can be summarized as follows:

• At the anode: 2Cl^- → Cl₂ + 2e^-
• At the cathode: 2HO + 2e^- → H + 2OH^-

The overall reaction for the electrolysis of NaOH can be represented as:

2NaOH (aq) → Cl₂ (g) + H₂ (g) + 2NaOH (aq)

In contrast, when we electrolyze molten sodium chloride, the process is different. The NaCl does not contain water, so the ions are free to move in the molten state. At the anode, chloride ions are oxidized to form chlorine gas, and at the cathode, sodium ions are reduced to form sodium metal:

• At the anode: 2Cl^- → Cl₂ + 2e^-
• At the cathode: Na⁺ + e^- → Na (s)

The overall reaction for molten NaCl can be summarized as:

2NaCl (l) → Cl₂ (g) + 2Na (s)

Key Differences

The key difference between these two processes lies in the presence of water in the NaOH solution, which facilitates the production of hydrogen gas. In molten NaCl, the absence of water means that sodium metal is produced instead of hydrogen.

Electrolysis of Sulfuric Acid: Concentrated vs. Dilute

When we consider the electrolysis of sulfuric acid, the concentration of the acid significantly affects the products formed. In dilute sulfuric acid, the primary reactions involve the water molecules rather than the sulfate ions. Here’s how it works:

• At the anode: 2H₂O → O₂ + 4H⁺ + 4e^-
• At the cathode: 2H₂O + 2e^- → H₂ + 2OH^-

The overall reaction for dilute sulfuric acid can be summarized as:

2H₂O (l) → O₂ (g) + H₂ (g)

On the other hand, in concentrated sulfuric acid, the electrolysis process is different. The sulfate ions are less likely to participate in the reaction due to the high concentration of H⁺ ions. Instead, the water molecules are still involved, but the products differ:

• At the anode: 2H₂SO₄ → 2H₂O + O₂ + 2SO₂ + 4e^-
• At the cathode: 2H₂O + 2e^- → H₂ + 2OH^-

The overall reaction for concentrated sulfuric acid can be summarized as:

2H₂SO₄ (l) → O₂ (g) + H₂ (g) + SO₂ (g)

Understanding the Differences

The main distinction here is that in dilute sulfuric acid, the electrolysis primarily produces hydrogen and oxygen gases from water, while in concentrated sulfuric acid, the presence of more sulfate ions leads to the formation of sulfur dioxide along with oxygen and hydrogen. This showcases how concentration can drastically alter the electrolysis products.

In summary, the electrolysis of different substances and under varying conditions can yield a variety of products, illustrating the importance of understanding the underlying chemical principles at play.