Which of the following substances is a heavy chemical?

Analyze the question: You're asked to identify which substance is classed as a "heavy chemical" in industrial chemistry.

Concept: Heavy chemicals

In industrial chemistry, heavy chemicals are inorganic chemicals produced on a very large scale (thousands of tonnes per year) and used as raw materials for making many other products. They are usually made in bulk and are relatively cheap.

Classic examples:

• Tetraoxosulphate(VI) acid, H₂SO₄ (sulphuric acid), the "king of chemicals"
• Sodium hydroxide, NaOH
• Sodium trioxocarbonate(IV), Na₂CO₃ (soda ash)
• Nitric acid, HNO₃
• Ammonia, NH₃, and chlorine are also produced in huge quantities and are sometimes listed among them

Evaluate the options:

• A. Ammonia: Made in bulk by the Haber process, and in some textbooks it is listed as a heavy chemical. However, it is usually treated as a gas used for fertilizer production, and WASSCE-type questions typically choose the acid as the standard example.
• B. Barium hydroxide: A laboratory reagent, not produced on an industrial bulk scale.
• C. Hydrochloric acid: Mostly a by-product or laboratory/industrial reagent. It is not the classic heavy chemical example.
• D. Tetraoxosulphate(VI) acid: Produced by the Contact process on a massive scale and used in fertilizers, detergents, paints, batteries, and more. It is the standard textbook example of a heavy chemical.

Answer: D.

Exam tip: When you see "heavy chemical," think of H₂SO₄, NaOH, and Na₂CO₃. Sulphuric acid is the most common one in WASSCE and JAMB questions. Remember that "heavy" refers to the huge quantity produced, not the weight of the substance.