Question

The decreasing order of acidic nature of perchloric acid, sulphuric acid and sodium bisulphate is (1) sulphuric acid \(>\) sodium bisulphate \(>\) perchloric acid (2) sodium bisulphate \(>\) sulphuric acid \(>\) perchloric acid (3) perchloric acid > sodium bisulphate \(>\) sulphuric acid (4) perchloric acid > sulphuric acid \(>\) sodium bisulphate

Short answer

Option (4): perchloric acid > sulphuric acid > sodium bisulphate

Step-by-step solution

- Identify the Acids

The acids in question are perchloric acid (HClO4), sulphuric acid (H2SO4), and sodium bisulphate (NaHSO4).

- Determine Acid Strength

Perchloric acid (HClO4) is one of the strongest known acids, while sulphuric acid (H2SO4) is also very strong but slightly less than perchloric acid. Sodium bisulphate (NaHSO4) is a salt that can behave as an acid in water, but it is weaker than both perchloric and sulphuric acid.

- Rank the Acids by Strength

Based on their acid strength, the order from strongest to weakest is: perchloric acid (HClO4) > sulphuric acid (H2SO4) > sodium bisulphate (NaHSO4).

- Match with Given Options

From the given options, the correct order is that perchloric acid is stronger than sulphuric acid and sulphuric acid is stronger than sodium bisulphate. This matches option (4).

Key concepts

Perchloric Acid

Perchloric acid, or HClO4, is recognized as one of the strongest acids known today. Its high acidity is due to its ability to completely dissociate in water, releasing a significant amount of hydrogen ions (H+). This complete dissociation helps to drive many chemical reactions and makes it a crucial reagent in a variety of industrial and laboratory processes.
Perchloric acid is often used in etching, metal processing, and the manufacturing of salts like ammonium perchlorate. Despite its strong acidic nature, HClO4 must be handled with extreme care due to its highly reactive and potentially explosive properties, especially in the presence of organic materials.

• Complete Dissociation: Perchloric acid dissociates fully in aqueous solutions, making it a strong acid.
• Applications: Used in metal processing and the production of ammonium perchlorate.
• Safety: Handle with care; it is highly reactive and potentially explosive with organic substances.

Sulphuric Acid

Sulphuric acid (H2SO4) is another powerful acid but slightly less than perchloric acid. It is classified as a strong acid because it dissociates completely in aqueous solutions, releasing a high number of hydrogen ions (H+).
Sulphuric acid is widely used in industrial applications, such as the production of fertilizers, the processing of mineral ores, and in the petroleum industry for refining oil. One key property of H2SO4 is its strong dehydrating nature, which is why it is often utilized in synthesis reactions and drying processes.

• Complete Dissociation: H2SO4 fully dissociates in water, which categorizes it as a strong acid.
• Industrial Use: Commonly employed in fertilizer production and oil refining.
• Dehydration Property: Useful in drying processes and synthesis reactions.

Sodium Bisulphate

Sodium bisulphate, also known as NaHSO4, is a salt that can act as an acid in aqueous solutions. However, its acidic strength is much weaker compared to perchloric acid and sulphuric acid.
When NaHSO4 dissolves in water, it releases hydrogen ions (H+) and sodium ions (Na+), contributing to its acidic nature. Due to its relatively lower acidity, sodium bisulphate is often used as a pH adjuster in swimming pools, household cleaners, and in laboratory settings where a mild acid is required.

• Weak Acid Nature: Sodium bisulphate is much weaker than perchloric and sulphuric acids.
• Disassociation: In water, it releases H+ and Na+ ions, acting as a mild acid.
• Common Uses: Used in pH adjustment for pools, cleaning products, and mild acid applications.